The Obama administration has launched a quiet campaign over the past two months to seize from local officials a key drug used in lethal injections -- part of a spreading investigation that has contributed to a de facto death penalty freeze in several states.

The investigation stems from concerns about the overseas source of the drug, though some question whether those concerns make a handy excuse to slow the pace of executions. The seizures started in Georgia, where the Drug Enforcement Administration in March grabbed their supply of sodium thiopental. From there, the DEA swooped into Tennessee, Kentucky and other states to confiscate their stash, forcing the states to either find an alternative chemical or suspend executions.

"It's very strange," said Kent Scheidegger, legal director with the Criminal Justice Legal Foundation.

Sodium thiopental is just one drug in a three-drug mix used to execute prisoners. It is used as the first drug in the process to induce general anesthesia. The subsequent drugs paralyze and then kill the inmate.

The administration is keeping its probe under wraps. Though the DEA said in March they had "concerns" about the way the drug was imported into the United States, federal officials have since stopped talking about it entirely. The DEA referred questions from FoxNews.com to the Justice Department. A representative at the Justice Department said she could not comment on the case.

State officials confirm the circumstances of the seizures.

Lauren Kane, a spokeswoman with the Georgia attorney general's office, told FoxNews.com officials seized their state supply and that while the justice system can continue to work on death penalty cases, for the time being the executions themselves "cannot be performed."

In Georgia, concerns were being raised about the drug before it was used in January to execute Emmanuel Hammond, who was convicted in the 1988 murder of a teacher. The Southern Center for Human Rights complained that documents showed Georgia bought the drugs from the "back room" of a London driving school, claiming there were "serious questions" about whether the drug was expired or even real. Then another attorney for a death row inmate in February requested a federal investigation -- raising concerns about the circumstances of the purchase, accusing the state of potentially breaking the law by failing to register the import. The attorney warned that a proper dose is critical to ensure the subject does not experience "intense pain."

Before these red flags were raised, the lone U.S. manufacturer of the product had set off a scramble at the state level when it suspended production in 2009 and then announced in early 2011 that it would stop production permanently. The shortage has delayed and disrupted executions in several states, forcing them to find alternative drugs or overseas sources for sodium thiopental -- the problem was compounded after Britain, one of those sources, banned the export of the product and then the Justice Department started seizing it.

From Georgia, the DEA moved on to Tennessee, Kentucky and elsewhere.

Dorinda Carter, with the Tennessee Department of Correction, said the state turned over its "entire supply" at DEA request in late March.

"They had some concerns about our domestic vendor's import procedures," she said, without elaborating. Carter said the state has executions scheduled this fall and is "looking at other options."

The DEA also seized Alabama's supply. State Department of Corrections spokesman Brian Corbett said the state had obtained a "small amount of sodium thiopental" from Tennessee, but was contacted by the DEA "within a week" of getting the supply.

"The Alabama Department of Corrections willingly turned over to the DEA all of the sodium thiopental it had received from Tennessee and no longer has it in its possession," Corbett said.

"The Alabama Department of Corrections has in the past, and will in the future if asked, cooperate fully with federal authorities to the extent requested. I cannot provide further information at this time."

Scheidegger said the Justice Department is overreaching, effectively halting the use of a drug that the Food and Drug Administration -- the agency "with primary responsibility" -- has left alone.

"This is interference in a core function of state government," he said. Scheidegger added that amid concerns about sodium thiopental, most states will probably end up moving to alternative drugs. States like Ohio have already moved to pentobarbital to execute inmates. Corbett said Alabama has just changed its policy to allow for pentobarbital as well. And Texas, which leads the nation in executions, just executed a prisoner Tuesday using pentobarbital. South Carolina followed suit Friday.

But Scheidegger suggested the administration could have an underlying motive in forcing states to find a new method.

"The DEA is part of the Department of Justice and we know the head of the Department of Justice doesn't like the death penalty," he said.

The Justice Department did not return a request for comment on the intent of the seizures.

Attorney General Eric Holder does not personally support the death penalty, though he has authorized his prosecutors to seek it since taking office. President Obama also spoke out against capital punishment before he was president, but has since said it should apply in severe cases -- he even said during the 2008 campaign that he disagreed with a Supreme Court ruling that would prohibit the death penalty for child rapists.

Statistics kept by the Death Penalty Information Center show the pace of executions under Obama has slowed slightly. There were 96 executions in the first two years of his presidency, compared with 130 during the first two years of the George W. Bush administration. Throughout that period, the number of death row inmates has stayed relatively constant -- there were nearly 3,600 prisoners on death row in 2001, dropping to nearly 3,300 in 2009.

Though the Obama administration has started to scrutinize the process with its DEA investigation, it's far from clear whether that's part of a broader anti-death penalty strategy. In fact, the Justice Department just weighed in against death row inmates in a key case involving sodium thiopental.

In that case in District of Columbia federal court, six death row inmates criticized the Food and Drug Administration for allowing the drug to be imported into the country and called on the agency to step in and block future shipments.

"Thiopental is an unapproved drug, a misbranded drug and an adulterated drug," the plaintiffs said in the complaint, claiming that imports "greatly" increase the risk that inmates would not be properly sedated.

The Justice Department, though, filed a motion urging the judges to dismiss the suit, arguing that the FDA has the right "not to refuse admission to thiopental for use in capital punishment."

A Justice Department representative did not respond to a question from FoxNews.com about why the department would on one hand investigate the drug, while at the same time fight a lawsuit that raised questions about the drug.

The motion, though, gave a hint. Justice attorneys mentioned the importance of giving "deference to law enforcement on matters involving drugs for use in capital punishment," suggesting the FDA was not suited to investigate such a matter.

Syndicated columnist Debra Saunders suggested the Justice Department, regardless of the court case, is trying to at least slow the pace of executions -- she said it "speaks volumes" that the department hasn't raided California, which has had executions on hold anyway and just announced it was delaying executions for at least another year.

"States have death penalty laws, and the federal government is trying to make it harder for the states to execute those laws," Saunders said.