Railroad crews continued removing wreckage yesterday and Metro workers started rebuilding track just north of the Takoma subway station, the site of a 21-car freight train derailment early Friday.

Investigators for CSX Corp., operator of the train, had not determined the cause of the 4:30 a.m. accident, which caused no injuries but tore up chunks of parallel railroad and Metro track, cutting off the public transit system's rail service to the Takoma and Silver Spring stations at least through the weekend.

Metro officials planned to decide today whether to resume rail service by tomorrow morning's rush hour. The transit agency again provided free shuttle bus service yesterday from the Fort Totten Red Line station to Takoma and Silver Spring, and it planned to offer it again today.

The trip from Silver Spring to Fort Totten, which normally takes 10 to 15 minutes by Metrorail on a Sunday, is expected to take 20 to 30 minutes on the shuttle bus today.

"The work has progressed very well," CSX Baltimore division manager Dan Smirl said yesterday as plows ripped up damaged rail and wooden ties and cranes piled the debris onto trucks for removal. Crunched freight cars were lifted onto wheels to be taken away by rail.

Smirl estimated the damage to about 1,600 feet of railroad track at $25,000. Damage to the freight cars, part of a 134-car train carrying automobiles, food and paper, was estimated at $200,000. The only visible damage to the contents was the crushed front end of one automobile seen through a set of buckled freight car doors, according to CSX's local freight damage manager, who was at the scene.

CSX planned to replace its track immediately and begin using it by late today, Smirl said. The damaged track lies on the west side of Metro's tracks; another CSX track, which was not damaged, lies on the east side.

About a dozen freight trains travel the west track each day, but Smirl said the railroad incurred no disruption in service because it could continue to use the east track.

By yesterday afternoon, CSX had cleared the 10 derailed freight cars that had crashed onto Metro property, tearing down 1,500 feet of fence and affecting about 800 feet of Metro track.

As the CSX cars were pulled away, Metro was able to inspect damage to its tracks more carefully and to begin repair work, said spokesman Allen Long. "We're working around the CSX people," he said.

Metro had no estimate yesterday of its damage costs, Long said. Although the inbound Red Line track clearly was broken and bent, Metro officials said that the outbound track appeared to have received little damage.

CSX investigators were examining all the damaged track, cars and operating information to determine the cause of the wreck, said spokesman Charles Castner.

"As far as I'm concerned, that is some of the best track you could look at," Smirl said. CSX crews last week performed routine maintenance work on the track, resurfacing it and working on its road bed, he said.

Takoma Park residents turned out yesterday to watch the repair work, snap photographs of the wreckage and talk about living so close to the train tracks.

One neighbor gestured toward a rail car lying on the grass next to a house at the end of Chestnut Street. "There used to be a house there," he said. "But they cleared it when they widened the tracks to make room for Metro."