A suspect in last year's March 11 Madrid train bombings had a sketch and technical details about Grand Central Terminal (search) in New York City but U.S. officials said Wednesday there was no immediate threat to the famous railroad station.

The sketch and data were on a computer disk seized about two weeks after the train bombings that killed 191 people last year, the Spanish newspaper El Mundo first reported.

New York Police Commissioner Ray Kelly (search) said in a Wednesday press conference that the information gained did not appear to be part of a grand plan.

"The material has been linked to individual involved in the Madrid bombings," Kelly said. "However, we have no information to indicate that these drawings were part of an operational plan to attack Grand Central station."

The material also included photographs, and a drawing of a private building in the city, which Kelly refused to identify.

New York Mayor Michael Bloomberg (search) said the FBI had informed the Police Department about the existence of the data on the computer and the city responded by tightening security at transit centers.

"We've known about the data on the computer for a long time," said Bloomberg, interviewed on WBLS Radio. "We've taken the appropriate steps 'back when' to beef up security at all of the major transportation hubs — train stations and airports and bus stations, places where you say if a terrorist wanted to attack, they would."

Officials said it's no surprise, however, that terrorists are trying their hardest to hit the United States again.

"We've known for a long time there are a number of targets in the U.S. ... but to have found something in the detail that it exists is a little disturbing," Bill Gavin (search), president of The Gavin Group and former assistant FBI director, told FOX News on Wednesday. "It will certainly heighten everybody's awareness in New York ... it's not a matter of if, it's a matter of when."

Rep. Jane Harman (search), the ranking Democrat on the House Select Committee on Intelligence, noted that New York City officials, as well as others around the country, have done "huge amounts" of work since Sept. 11 to make sure this country isn't attacked again.

"That's the good news story but the bad news story is, we need to stay prepared and in our view, our homeland security effort is sorely lagging," she said, referring to a lack of an effective national security alert system, among other things.

Harman said there's no longer one central group trying to attack the United States but another type that's far more frightful.

"We do know there's a number of groups now — they're not all Al Qaeda — that are loosely affiliated, a sort of horizontal structure. That's very dangerous, they could cause us harm," Harman said

"Our operating presumption has to be that they're looking for the best way to do that and we need to be prepared 24-7 and we need to be prepared in the right way."

Gavin, Harman and others said rail, subway and port security have, since the Sept. 11 attacks, been major areas of concern for potential terrorists activity.

"These are just terribly vulnerable spots and they need some real attention and some innovative ways to provide protection to them," Gavin said.

Spanish police turned the disk over to the U.S. agents from the FBI and CIA in December once they understood the scope of the technical data, the report said.

On Wednesday at Grand Central, visible security seemed at its usual high level, with National Guard, machine-gun-toting law enforcers and bomb-sniffing dogs.

"I'm used to this," said Elaine Weaver, a tourist from Bristol, England, who was passing through the terminal. "We're used to bomb scares everywhere. So you're careful but it doesn't deter me."

A U.S. Embassy official confirmed that American law enforcement authorities received information related to Grand Central Terminal from Spanish authorities in December.

A government source confirmed to FOX News that a sketch was passed on by Spanish investigators to the FBI. It was not a photo, or technical drawing, but a single sketch that was so rough it appeared to be Grand Central. The government source added that there is no imminent threat.

There were conflicting descriptions of what the drawing showed. A Spanish police official said it depicted a facade similar to that of Grand Central; New York police said it showed a large interior room off the terminal's main concourse.

The same Spanish official, who spoke on condition of anonymity, confirmed the sketch was found in the home of Mouhannad Almallah, a Syrian who was arrested in Madrid on March 24 but later released, although he is still considered a suspect.

Almallah was questioned over his alleged ties to two suspects jailed in connection with the attack after witnesses placed them aboard trains targeted in the string of 10 bombs, El Mundo said.

A total of 24 people are in jail over the attack, although at least 40 more who were arrested and released are still considered suspects.

After the Madrid attack, security around New York City's subways and commuter points, such as Grand Central and Penn Station, were ratcheted above the already-high post-9/11 levels.

Peter Kalikow, chairman of the Metropolitan Transportation Authority, said at the time that the chance of a transit attack in New York was "diminished, but possible." He added that if an emergency occurred, "100 guys would show up right away." He refused to disclose exact numbers.

Kalikow also said the MTA's chief of security had been in London at the time of the Spain bombing and was sent to Madrid to observe the situation.

FOX News' Catherine Herridge, Liza Porteus and The Associated Press contributed to this report.