After four days on high alert, police announced Monday that they were scaling back a New York City (search) subway security crackdown prompted by a report of an Al Qaeda plot to blow up trains.

Officials said they were still investigating claims by an informant that Al Qaeda (search) operatives in Iraq had hatched a plot to attack the subways using baby strollers packed with remote-controlled explosives. They continued to defend a decision to flood the subways last Thursday with thousands of extra police officers.