Penn Station has resumed normal operation after authorities shut it down earlier today. New terror threats have put The Big Apple on edge, and security in New York City is on high alert.

Authorities briefly closed part of Penn Station on Friday and commuters headed to work under the watchful eyes of police after a newly disclosed terror threat against the New York subway system.

A discarded soda bottle filled with an unidentified green liquid was found at the station during morning rush hour, Amtrak officials said. The substance did not pose a threat to passengers and was removed for testing.

Officials in New York revealed the threat Thursday, saying an FBI source warned that terrorists had plotted to bomb the subway in coming days. But Homeland Security officials in Washington downplayed the threat, saying it’s of “doubtful credibility.”

President Bush maintained that New York acted alone in unveiling the threat, but he wasn’t second guessing their decision nor was he suggesting they overreacted.

“Our job is to gather intelligence and pass it on to local authorities. And they make the judgements necessary to respond,” Bush told reporters. Administration security officials had said on Thursday the threat to New York was of “doubtful credibility,” a phrase repeated earlier Friday by Bush’s spokesman.

“The level of cooperation between the federal government and the local government is getting better and better. And part of that level of cooperation is the ability to pass information on. And we did, and they responded,” Bush said during a picture-taking session at the White House with the prime minister of Hungary.

Asked if he thought New York officials had overreacted, Bush said: “I think they took the information we gave and made the judgements they thought were necessary. And the American people have got to know that, one, we’re collecting information and sharing it with local authorities on a timely basis. And that’s important.”

The Counterterrorism Blog continues to provide great coverage of this story.