New York ? Details surfaced about an alleged plot to attack the city’s subways with bombs hidden in bags and possibly baby strollers as local and federal officials jostled over the credibility of the threat.

A Department of Homeland Security memo obtained by The Associated Press said the attack was reportedly scheduled to take place sometime today or in the coming days, with terrorists using timed or remote-controlled explosives hidden in briefcases, suitcases or in or under strollers.

The memo said that the department had received information indicating the attack might be carried out by “a team of terrorist operatives, some of whom may travel or who may be in the New York City area.”

The memo, issued Wednesday to state and local officials, said that homeland security and FBI agents doubted the credibility of the information, but it provided four pages of advice about averting a possible attack.

New York City police officers patrol at Grand Central Terminal in the early morning hours Saturday in New York. Security in the mass transit system has been increased following announcement of an alleged plot to attack the city's subways.

Police fielded 134 suspicious package calls Friday, up from 42 the day before the threat announcement. One call reported a bubbling green liquid in a soda can that closed part of Penn Station Friday. Police continued to race around the city to check on plastic bags and sacks of garbage Saturday.

The department will dispatch several teams of counter-terror officers to Game 4 of the American League playoffs between the Yankees and Los Angeles Angels, which was rained out Saturday and rescheduled for Sunday night. The police force’s so-called “Atlas teams” will board trains bound for the game and patrol around the stadium.

City officials said they noticed no fluctuations in subway ridership Friday or Saturday, although a transit spokesman said exact figures would not be available for a month.