A Metro subway train carrying a handful of employes sent eight track repairmen scrambling for a tunnel wall early yesterday morning when it roared unannounced into a work site near the Rosslyn station and struck heavy equipment.

The accident, which left four Metro employes slightly injured, resulted in delays of up to 20 minutes for subway riders on the Blue and Orange lines during most of the morning rush hour yesterday.

"This happened because somebody screwed up; we just haven't figured out who yet," said one disgusted senior official. A board of inquiry was established yesterday to find out exactly how the 4:56 a.m. incident occurred.

One track repairman, identified by officials as Blondell Edwards, was credited with possibly saving the lives of his colleagues by shouting that a train was coming. Officials estimated the train was traveling at about 45 m.p.h. when it struck the equipment.

The incident occurred on a section of track where the third-rail power to drive the train had been disconnected. However, because of an unexplained foul-up in signaling, the train was coasting downhill into the work site without power. The automatic system that controls train speed and braking was functioning, officials said, but simply had not been given the proper information.

"It looks like a human error," said Nicholas Roll, Metro's assistant general manager for transit services. Such an incident would highly improbable during normal subway operating hours because the track maintenance that was being done requires closing a section of line -- work that Metro does during off-hours.

It took almost three hours to clean up the area after the accident occurred in the Rosslyn-bound tunnel between Arlington Cemetery and Rosslyn. During that time, trains were routed around the site on the single remaining track, a process that causes delays.

All of the Metro track repairmen were able to walk out of the tunnel to the Rosslyn station. The injuries reported by the four men were described as minor; none were hospitalized. Four train operators riding the train were not hurt.

Four subway cars were damaged slightly as they struck and then dragged the track repair equipment.

Normal procedure, according to Metro officials, would have been for the trackside signal closest to the work site to have been set on red. Instead, the signal was white, which means that all is clear.

The work crew also is expected to set out warning lanterns and flags to tell a train operator of work ahead. "We don't have to take as many precautions when we think we're not in a traffic area," said Ralph E. Smith, director of general maintenance for Metro.

Metro's passengers seemed to take the delays in stride with a minimum of grumbling. Because of the one-way operation on the track, Metro would run three trains in one direction, then three trains in the other. That meant that larger-than-normal crowds of people piled up on platforms -- particularly at the Pentagon and Ballston stations as bus passengers arrived.

At the Rosslyn station, where Washington-bound trains were arriving on the Virginia-bound track on the lower level, there were complaints about a lack of announcements in the station. Several times people clattered down the escalators at breakneck speed to catch an inbound train after having waited for five or 10 minutes on the upper level.