New Yorkers shrugged off fears of exploding baby carriages and went about their weekend routines Saturday as authorities debated whether a reported subway terror plot was a legitimate threat or an overblown hoax.

"It's kind of like you're used to it by now," said Erica Ouda, 19, as she boarded a 4 train in lower Manhattan. "There's always a threat."

A Department of Homeland Security (search) memo warned this week that a team of terrorists may have traveled to New York to put remote-controlled bombs in briefcases and baby carriages in an attack on or around Sunday. It cautioned that the FBI (search) and Homeland Security doubted the threat's credibility.

But as U.S. forces interrogated three suspects in Iraq, New York officials said they felt even more confident about their decision to ramp up patrols and bag searches in the subways.

"We've over the last couple of days become more convinced that the threat was real," Mayor Michael Bloomberg (search) said.

Homeland Security Secretary Michael Chertoff (search) said Bloomberg was right to err on the side of caution.

"The secretary respects the mayor's judgment and believes that the security precautions being taken by Mayor Bloomberg and other New York officials are absolutely an appropriate response," he said in a statement.

An overseas tipster told U.S. intelligence last month that three men were plotting a coordinated bomb attack on the country's subways, law enforcement officials said. The tipster passed parts of a lie-detector test, and U.S. forces in Iraq arrested three suspected plotters earlier in the week.

With two of the men captured and the plot presumably disrupted, Bloomberg announced Thursday that security was being heightened in the subways. Thousands of extra officers were dispatched into the system and the number of bag checks doubled.

Almost as soon as the threat was made public, officials in Washington began talking it down, and Homeland Security still downplayed the threat Saturday.

"We continue to work with the intelligence community and officials at all levels of government," department spokesman Russ Knocke said. "Although the threat information was very specific, it still remains of doubtful credibility."

Paul Browne, the police department's chief spokesman, declined to discuss any new information from Iraq, but said the department felt vindicated.

"As the days have progressed, it just reinforces the decision made to increase the security in the subway system," he said.

New Yorkers responded to the government jostling with a mix of skepticism and resignation, saying they didn't believe there was a threat or they had no other way to get around town.

Some said the rhythm of threat, police response and no attack had become just another element of life in the city since the 2001 terrorist attacks at the World Trade Center.

"If something was going to happen, it would have happened already," said Shanti Stevenson, 20.

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 (search) 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.