NEW YORK -- New York Mayor Michael Bloomberg and city police are not convinced that last week's alleged subway bomb plot was a hoax.

CNN and the New York Post, citing unnamed sources, report that an informant in Iraq has admitted he made the whole story up.

The informant had claimed that al-Qaida operatives in Iraq were plotting to attack the city's subways using baby strollers packed with remote-controlled explosives. The reported threat said the attacks could occur as early as last Friday.

Bloomberg said the informant passed a lie detector test.

Police Commissioner Raymond Kelly said the informant could not have recanted because he's not in custody. In fact, Kelly said U.S. officials have lost track of him.

New York City's heightened subway security will slowly scale back to what it was before officials announced the supposed subway bombing threat last week.

Kelly stressed that police will continue random bag searches in the subways that began in response to the bombings on the London transit system.