Commuters awaiting trains were evacuated from the station because of heavy white smoke that shut down the Long Island Rail Road and the 7th Avenue subway line around 3:45 p.m., officials said. No injuries were reported.

Firefighters believed the fire was caused by a live wire touching a train wheel. The fire was extinguished within minutes, but it created a "smoke condition" under Platform 11 at tracks 20 and 21.

LIRR spokesman Brian Dolan said limited eastbound service -- from tracks 13-16 -- was restored at 7:02 p.m. Normally, 21 tracks would be used. Limited westbound servuce was restored at 7:45 p.m.

"They're not operating on a regular schedule -- we're loading trains until they're full and then sending them on," he said.

The cause of the fire is under investigation by fire and police officials as well as Amtrak, which maintains and operates the facility.

Twelve fire units, or about 60 firefighters, and several ambulance companies were on the scene after the fire broke out, said fire spokesman Mike Loughran. Station workers shut off electricity to tracks 18 to 21 so the firefighters could work.

The smoke caused firefighters and police to evacuate the station's lower mezzanine at 3:48 p.m., sending hordes of Valentine's Day commuters into the streets surrounding Madison Square Garden. Some were shielding roses from the crush of people.

The heavy smoke also caused subway service on the 7th Avenue 1, 3, and 9 lines to be suspended in both directions, officials said. The subways were being diverted until the smoke condition could be cleared. Other subway lines were running normally.

By the rush hour, Amtrak trains were experiencing some delays and were being diverted, and New Jersey Transit trains were running on schedule, officials said. Passengers could get to them from Penn Station from an area unaffected by the smoke.

It was a different story for LIRR passengers, who were told to take subways to Jamaica to pick up Nassau- and Suffolk County-bound trains.

That's what Geralyn Brown of Copiague said she was reluctantly doing. The 36-year-old union employee said the crisis might jeopardize her Valentine's Day dinner with her boyfriend.

"So much for my dinner plans," Brown said.

Another passenger, Tracie Hotwit, of Edison, N.J., was having better luck. Because New Jersey transit was running from the station, all she needed to do was maneuver through the throngs seeking to alight from the musty underground.

"I was expecting to get home a little earlier," said Hotwit, who on Saturday will be holding her wedding shower. "This is putting a little crimp in the preparations."

At the Jamaica LIRR station, where transit officials directed all travelers to pick up their commutes, the trains had been severely delayed. By about 7:45 p.m., they were departing and arriving frequently, though not yet on a regular schedule.

Still, train platforms remained packed with would-be passengers. Among the passengers were many with fresh flowers for their loved ones on Valentine's Day.

"Now my roses are crushed and they're dying," said Chris Betro, 29, of Lindbrook, who had been trying to take a 4 p.m. train from Manhattan but ended up scrambling to catch a 7:20 p.m. train in Jamaica.

He was carrying 12 red roses for his wife and had taken more than two hours to get to Jamaica station. He said he was "insane" because of the delays.

In light of recent terror warnings, one passenger initially was afraid.

"Somebody was yelling, 'Evacuate.' It was kind of scary," said Cindy Flagg, 27, of Central Islip, who had been awaiting departure on a train when train officials evacuated Penn Station.

She spent more than four hours getting from Penn to Jamaica before boarding a train for home. "Me and my husband were going to catch a movie and have dinner," she said. "Now I'll just be happy to be home."

Harold Bennett, 30, of Brentwood, whose wife is due to give birth to their first child this summer, was rushing home to cook dinner with her for Valentine's Day. She was forced to start cooking without him.

"We were supposed to cook a little dinner and enjoy each other's company," he said as he held a half-deflated, heart-shaped balloon reading "I Love You," a white teddy bear and an "I Love Lucy" DVD in a red gift bag. "But now I'm forced to wait."