A damaged section of the Baltimore-Washington Parkway near Laurel was still closed to traffic last night as construction crews worked to repair a sinkhole that opened Friday morning beneath a stretch of the northbound lanes. But officials said the end of the job appeared to be in sight.

Officials with the U.S. Park Police said yesterday that contractors had underestimated how much work would be needed to fix the roadway after heavy rain compromised the roadbed just north of Route 32 and caused a collapse.

Although officials said Friday that they had hoped to reopen the road by early yesterday, they later began adjusting their predictions. A park police spokesman said last night that officials expected that the northbound lanes could be open by early this morning. The southbound lanes are open.

Park Police Sgt. Scott Fear said the timetable had been delayed because "they've hit some complications. They need to do more than they thought. It's not a science."

By 9 p.m., Fear said, the damaged section was being repaved, meaning that the work was in its final stages.

The collapse forced the closure of a two-mile section of the parkway between routes 32 and 175. Traffic was still diverted onto Route 1 and Interstate 95 yesterday, prompting one official to caution, "If you can avoid the area altogether, you'll be much better off."

The advice provided little comfort to motorists driving north for weekend activities, such as getting to Baltimore-Washington International Airport and a 1 p.m. Baltimore Orioles game at Camden Yards.

By yesterday afternoon, speeds were down on I-95 and congestion up.

"It's been a nightmare," said Maryland State Police Sgt. D. Vinson of the Waterloo barracks in Howard County. "It's all the airport traffic from D.C. and [cars headed to the] Orioles game. There have been a lot of rear-end collisions and fender benders. . . . If we have to deal with this on Monday," he cautioned, "look out."

Hoping to relieve congestion on side roads, the Maryland State Highway Administration retimed traffic signals on Route 1 to give more green, officials said.

Officials blamed the sinkhole on the arrival of rain just as the U.S. Army Corps of Engineers was tunneling utility wires beneath the parkway in a project tied to nearby Fort Meade. The $500,000 project, linking defense contractors west of the parkway to the fort on the east, was routine, officials said.

But as heavy rain trailing Tropical Storm Cindy struck, soil underneath the left edge of the road started to give way. By Friday morning, it was visibly eroding.

Officials said eagle-eyed U.S. Park Police officer Michelle Spencer spotted the erosion while the roadway was intact. Northbound traffic was diverted to parallel routes shortly before 11 a.m.

By Friday afternoon, a hole several feet deep and 15 to 20 feet wide could be seen.

"I'm sure a lot of experts will look at this when it's all over and ask, 'Is there anything we could have done differently?' " Fear said. "I'm sure if there is, it'll be done different" in the future.

Staff writers Philip Rucker and Martin Weil contributed to this report.