Federal investigators said yesterday they are focusing on crew members' handling of the four locomotives of the CSX Corp. freight train that derailed in Takoma Park early Friday in an incident similar to at least five other derailments on the same line in the last two years.

CSX and Federal Railroad Administration investigators stressed they have not determined the precise cause of the accident just north of the Takoma Metro station, where 21 of 134 freight cars derailed and severed Metro's Red Line service north of Fort Totten for three days. Metro was not running at the time and there were no injuries.

Metro resumed normal service yesterday after rebuilding 800 feet of track.

"We're focusing on how the crew handled the train," said Wendy M. DeMocker, a Federal Railroad Administration spokeswoman.

"That would involve braking, accelerating, speed, whether the cars were stretched out or bunched up."

Two of the locomotives were in front of the mile-long train, the other two in the rear.

According to industry safety experts, investigators are checking the possibility that the power settings on the locomotives were not coordinated.

If the front locomotives were braking while the rear ones were accelerating, the cars in the middle would be pushed together and could jackknife, one specialist said.

The longer the train the greater the danger, this expert said, because there is more slack between cars on longer trains, which amplifies the hazards of any accordion-like motion set up by the front and rear locomotives.

Railroad administration investigators said that, so far, they have found no problems with the wheels of the train or with the CSX track.

Nonetheless, they "have not ruled out equipment problems" such as faulty brakes or couplers, DeMocker said.

CSX spokesman Lloyd Lewis said the company would not comment on the investigation.

A federal source familiar with the investigation said the freight train was similar in configuration to at least five other CSX freight trains that have partially derailed along the CSX line through Western Maryland to Washington in the last two years.

CSX officials recalled two derailments of such trains in the area, one in Barnesville in 1985 and one in Boyds last year.

Both are western Montgomery County communities.

Railroad administration records show that a broken coupler was identified as the cause of the Boyds derailment. Another railroad administration report shows that a Sept. 25, 1985, derailment near Cumberland, Md., was blamed on sudden braking by the engineer.

Rear-end locomotives, called "pushers," often are used to provide extra power for long, heavy trains operating in hilly terrain. The CSX freight was carrying automobiles, auto parts, grain, flour and paper from Brunswick to Philadelphia.

Pusher locomotives generally are not necessary on the CSX line east of Sugarloaf Mountain in eastern Frederick County close to the Potomac River, the source said. At the time of the accident, the CSX train was running downhill at 42 miles an hour, well within the speed limit of 60 mph, the railroad administration said.

The CSX train was operated by six crew members -- three in the first locomotive, one in the second locomotive, and two in the third locomotive. The fourth locomotive was empty.

CSX did not test the crew for drugs or alcohol, citing railroad administration rules requiring such tests only in accidents involving a fatality or damage of more than $500,000. CSX has estimated the damage to track and cars at $225,000.

Metro, by contrast, tests bus and train operators for drugs or alcohol whenever operators are involved in any work-related accident or fight.

The speed of each of the four locomotives was recorded by equipment on board and will be used along with other information to analyze the accident and determine its probable cause, DeMocker said.

Investigators closely inspected the 1,600 feet of CSX track ripped up in the derailment, DeMocker said. "We have safely assumed that track had nothing to do with this accident," she said.

CSX was formed in 1985 by the merger of the Chessie System, which combined the old Baltimore & Ohio and Chesapeake & Ohio lines, and the Seaboard Coastline Inc. rail.