The terror threat that led authorities to heighten security for the New York City transit system was a hoax, a news report said Tuesday.

The report, posted on the CNN's website, quoted government sources as saying that an informant in Iraq told investigators about a terrorist plot involving New York's subway system, and after various investigations, officials determined the informant had given false information.

Law enforcement officials were quoted as saying on Monday they could not corroborate any of the informant's claims, which prompted the New York Police Department to scale back the increased security measures put in place on the city's subways last week.

The government sources said the three men arrested in Iraq with suspected links to the possible plot had been interviewed and underwent lie detector tests showing they knew nothing about such a plan, the report said.

New York Mayor Michael Bloomberg warned last Thursday that the city had received information from the FBI about a "specific threat," prompting the heightened subway security.

The threat mentioned Friday and Sunday as possible days that an attack might occur, according to the report.

Bloomberg questioned reports on Tuesday that the bomb plot 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 by CNN and a New York newspaper.

Source: Xinhua