New York ? Mayor Michael Bloomberg and police officials questioned reports on Tuesday that an alleged subway bomb plot that spread fear through the city was a hoax.

“I don’t know that it was confirmed that it was a hoax at all,” Bloomberg said when asked about the reports.

The reports, citing unnamed sources, claimed an informant in Iraq who had told U.S. authorities about the threat by al-Qaida later admitted he made it up.

The informant’s allegation prompted city and FBI officials last week to issue a dire public warning and to flood the subway system with thousands of extra police officers.

Police Commissioner Raymond Kelly, appearing with Bloomberg at a hospital groundbreaking in Harlem, said the informant could not have recanted because U.S. authorities in Iraq had lost track of him.

“As far as we know right now, the source is not in custody,” he said.