NEW YORK (CNN) -- New York City police said Monday they will reduce the increased security measures put in place last week on the city's subways."We're scaling back the levels to a heightened level that was in place prior to October 6," said New York Police Department chief spokesman Paul J. Browne .Browne said the security reduction was to begin Monday afternoon."Since the London bombings in July, the police department has added additional personnel and introduced bag inspections that will remain in place," he said."However, the added measures beyond that that were put in place after this latest terror threat were reduced."Law enforcement sources said last week the person who passed along the New York tip also gave information that prompted a military operation in Iraq, which led to the arrests of three al Qaeda suspects in Musayyib, about 45 miles south of Baghdad."We've been informed that as a result of the operation overseas that there were individuals captured and that they have not corroborated some of the earlier intelligence, and that's allowed us to scale back somewhat," Browne said.Government sources said Monday 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.New York Mayor Michael Bloomberg warned 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 an attack might occur, according to one official with knowledge of the investigation.Friday was three months to the day that four bombers carried out attacks on three London subways and a double-decker bus in which 52 people were killed and 700 wounded. (Full story)After Bloomberg's warning some intelligence officials played down the New York information, saying it was not credible.Browne said the specificity of the original intelligence left the police department "no choice" but to put in extra security measures.Bloomberg stood by last week's decision to increase security."Over the immediate future we'll slowly be winding down the enhanced security, but we, remember, stay at level orange in this city," the mayor told reporters Monday, referring to the advisory color denoting a "high" risk. "We have since 9/11, and we're going to take every single threat that has any chance of being credible seriously and do exactly what we did," Bloomberg said.