Construction workers labored under floodlights early this morning to shore up the top floors of the former William E. Miller furniture company building, after their threatened collapse caused police to close the area around Eighth Street and Pennsylvania Avenue SE to traffic.

Late last night, in what building inspectors said was the most critical operation in shoring up the building, two horizontal girders were positioned several feet above ground level without incident. Vertical girders were to be installed overnight.

Eastbound Pennsylvania Avenue SE remained closed between Seventh and Ninth streets and officials said they hoped to reopen that stretch and several other nearby blocks sometime today.

Authorities said a crack discovered in one of the building's brick supporting columns about 10 a.m. yesterday caused cracks in the brick facing above the north side of the top floor of the three-story structure.

The turn-of-the century building, a prominent landmark in the neighborhood around the Capitol East Metro station, was being renovated by owners who planned to convert it into retail, restaurant and office space, according to Leslie Riggs, a leasing agent for Dale Denton Real Estate.

The Miller company had occupied the building until last December, Riggs said. The owners were identified as J.C. Associates.

W. Monroe Stewart, chief D.C. building inspector, said late last night that he expected to decide by today whether the building could be saved, or whether safety considerations required its demolition.

"We're just standing by, hoping to save the thing and helping out any way we can," Stewart said shortly before midnight. "If it looks bad, however, we'll tell them to tear it down, because we don't want a building standing up that could fall down when people are walking by."

The cause of the cracks in the brick supporting columns, 4 feet wide by 2 feet thick, could not be immediately learned.

Stewart said the flaws might have resulted from the age of the building, or could be connected to cracks noticed several years ago at the time of Metro construction in the area.