Updated

Political commentator Rush Limbaugh (search) could become the target of a criminal probe into the sale and use of illegal drugs, sources told Fox News on Thursday.

Limbaugh, who quit his job as a football analyst for ESPN late Wednesday, had multiple sources from whom he could obtain the prescription drugs, namely OxyContin (search) and other painkillers, law enforcement sources said.

Reports in the New York Daily News and the National Enquirer alleged Limbaugh got the drugs from his housekeeper, Wilma Cline (search). But sources close to the investigation told Fox News that Limbaugh had other drug suppliers and said the popular conservative personality could face a criminal inquiry by the Palm Beach County (search) state attorney's office.

• Video: Rush Under Fire

Cline's attorney, Ed Shohat, told Fox News that "my client stands behind her story." Cline has been granted immunity from prosecution in exchange for her cooperation, a source told Fox News.

In a statement issued Thursday, Limbaugh said he was unaware of any investigation involving him. "No government representative has contacted me directly or indirectly. If my assistance is required, I will, of course, cooperate fully," he said.

The investigation apparently began as a probe into the illegal sale of prescription painkillers in South Florida that targeted dealers. But later investigators came across Limbaugh through clues gathered in a bust a Palm Beach County (search) in May, revealing him as a buyer.

The allegations were disclosed as Limbaugh dealt with the public relations storm that erupted over his comments concerning Philadelphia Eagles quarterback Donovan McNabb (search), race and the media. Limbaugh resigned Wednesday from ESPN's "Sunday NFL Countdown," the show where he made the comments.

One source told Fox News that Limbaugh was implicated by Cline and her husband David, and also by “other suppliers” whom the source did not name. The Enquirer paid the Clines a six-figure fee for their story, according to the source.

Asked about the culpability of Limbaugh, the source said that he could still face charges for having a large quantity of prescription painkillers without a prescription, but the source added that no charges are imminent.

OxyContin is a pain reliever that contains a very strong narcotic similar to morphine and is only intended for moderate to severe daily pain, according to the Food and Drug Administration.

Ed Shohat, a Miami lawyer for the Clines, said Thursday, "The Clines stand by the story." Shohat said neither he nor his clients would comment further.

Fox News' Orlando Salinas, Amy C. Sims and The Associated Press contributed to this report.