Nearly a dozen vehicles were involved in at least seven separate crashes after an apparent oil spill left the Outer Loop of the Beltway slick.
The accidents happened Friday morning between Connecticut Avenue and Rockville Pike.
Maryland State Police believe a dump truck lost its oil pan on the Outer Loop at Connecticut Avenue at about 6 a.m., but the truck kept driving, leaving a trail of oil in the far right lane of the Outer Loop.
A light misting of rain made conditions even worse, and the mess caused at least seven crashes and major delays. Driver Lamont Smith said his 15-minute drive turned into an hour-long commute.
"It was bad," Smith said. "No movement, and it was just bad."
Three people were taken to the hospital, fire officials say. Their conditions are not known at this time.