Southbound Interstate 5 reopened early Saturday afternoon after a pedestrian walking in the roadway caused all lanes to be closed for nearly 90 minutes.

The ensuing backup stretched for about 7 miles from 220th Street Southwest (Milepost 181) in Mountlake Terrace to nearly 128th Street Southwest. At least one collision occurred in the backup.

Washington State Patrol Trooper Rocky Oliphant said at 1:16 p.m. that the pedestrian had been “successfully detained” and that the road was reopening. He later clarified that the pedestrian had started speaking with troopers on scene before being taken into custody, and was later taken to a hospital.

The incident began late Saturday morning, when drivers described a shirtless man walking down the freeway. Oliphant said mental health professionals had been advised of the situation.

At 12:45 p.m., nearly an hour after the initial report, Oliphant said the man was still walking down the freeway and had crossed into King County. Troopers did not try to remove the him from the freeway, but followed him slowly, “attempting to communicate with him,” Oliphant said.

Law enforcement personnel were heard asking each other why the pedestrian had not been taken into custody. A request for comment sent to the Washington State Patrol was not immediately returned.

A driver on northbound I-5 told The Seattle Times he saw a large number of emergency vehicles following the shirtless pedestrian. The driver also reported seeing at least one collision in the southbound backup.