The latest terrorism arrests in New York were announced with the fanfare of a City Hall news conference, a dramatic photo of a broad daylight takedown by the police department and reassurance from local law enforcement officials that a serious threat had been neutralized.

Only one thing was missing: the FBI.

The FBI's glaring absence at the announcement and silence since then about the arrests of two men described by police as raving anti-Semites and would-be jihadists bent on attacking a synagogue raised questions Friday about the severity of the threat and the strength of the case.

The FBI and the Department of Justice have declined to explain the New York Police Department's assertion that the FBI-led Joint Terrorism Task Force, always a central player in past terror cases, was made aware of the investigation but decided not to get involved. And the U.S. Attorney's office in Manhattan, known for its successful prosecution of several high-profile terror cases for nearly two decades, also declined to comment.

But a law enforcement official briefed on the case said Friday that the FBI backed away because it had "reservations" about how it was conducted by the NYPD's Intelligence Division. The FBI also concluded it "wasn't a legitimate terrorism case," said the person, who wasn't authorized to speak publicly and spoke on condition of anonymity.

In the past, federal authorities have expressed concern about the Intelligence Division's tactics and its use of a cadre of undercover investigators like one used in the synagogue case.

The NYPD's top spokesman, Paul Browne, said Friday that any doubts about the investigation are unwarranted.

"When someone acquires weapons and plans to bomb the largest synagogue in Manhattan he can find, what do you call it? Mischief?" he said.

Rather than seek the usual federal conspiracy charges, the NYPD worked with the Manhattan district attorney's office to bring a case under an obscure state terrorism law that the office had never used before and that was viewed as symbolic when it was signed only six days after the Sept. 11, 2001, attacks. The case has been turned over to the office's Investigation Division, which has a history of prosecuting racketeering, cybercrime and money laundering cases — not terrorism.

Police Commissioner Raymond Kelly said Thursday that there was no evidence that the suspects, Ahmed Ferhani and Mohamed Mamdouh, were linked to al-Qaida or any other terrorist organization. But officials insisted the men posed a dire danger that had to be dealt with however possible.

"In today's fight against local, unaffiliated radicalized threat as we see here, intelligence and pre-emption are our keys," District Attorney Cyrus Vance Jr. said at the news conference. "And we must use all our tools at our disposal to neutralize these threats before local terrorists have the opportunity to act."

Ferhani and Mamdouh were arrested Wednesday on charges they wanted to strike a synagogue to avenge mistreatment of Muslims around the world. An undercover officer who investigated them reported that Ferhani wanted to become a martyr, and wiretap recordings caught the men calling Jews "rats" and other names.

Authorities say Ferhani, a 26-year-old Algerian immigrant, was nabbed in the sting buying guns, ammunition and an inert hand grenade. Mamdouh, a 20-year-old American citizen of Moroccan descent, was picked up a few blocks away.

The photo displayed at the news conference Thursday shows officers in NYPD jackets emerging from two unmarked cars to surround Ferhani's dark-colored sedan and arrest him.

Ferhani and Mamdouh were charged with conspiracy as a crime of terrorism, conspiracy as a hate crime and criminal weapons possession. Defense lawyers say the men deny the charges and claim they committed no crimes.

What's known publicly about the case so far suggests it "doesn't fit the model" of a typical federal terrorism prosecution, said Karen J. Greenberg, the executive director of the Center on Law and Security at New York University School of Law. "This was a gun case, not a WMD (weapons of mass destruction) case."

The allegations concerning the defendants' talk of harming Jews "are hate crimes," she added. "Whether or not it rises to terrorism, we'll see when it comes to court."

Police officials described the officer who interacted with the men for six months as a foreign-born recruit who was plucked from the police academy and placed in a little-known NYPD counterterrorism program that grooms and deploys young undercover officers to uncover potential plots.

The department has used graduates of the program to pose as devout Muslims, circulate among other men with radical leanings in the New York City area and, in some instances, secretly record their radical rants about fighting a holy war in the United States and abroad.

The undercover working the synagogue case is highly regarded and respected within the department for "his ability to handle the often stressful and demanding environment of intel operations," Browne said.

Last year, another one of the NYPD undercovers was credited with helping in the arrests in New Jersey of two men accused of trying to join up with the Somali terror group al-Shabab so they could kill Americans. Another was a key witness in the 2006 trial in Brooklyn of Shahawar Matin Siraj, convicted of plotting to blow up the Herald Square subway station in Manhattan, near where the Macy's flagship department store is located.

The New Jersey and Brooklyn cases landed in federal court. So did another similar case in Manhattan involving an FBI informant posing as a terrorist who offered cash to four down-and-out suspects to join a scheme to blow up synagogues in the Bronx and shoot down cargo planes at the Air National Guard base in Newburgh, about 60 miles north of New York City.

Agents arrested the men in 2009 after they planted explosive devices — fakes supplied by the FBI — in an elaborate sting operation staged in the Riverdale section of the Bronx. All were convicted last year.

Lawyers for the men had sought to get their convictions thrown out because of entrapment, arguing the government had "created the criminal, then manufactured the crime."

U.S. District Court Judge McMahon, in her ruling, said, "There is some truth to that description of what transpired here."

But the motion was denied.


Associated Press writers Colleen Long and Jennifer Peltz contributed to this report.