A driver was killed early Sunday in a single-vehicle crash in the Highway 99 tunnel near Mercer Street, the Seattle Fire Department said.

Emergency crews responded to the crash just after 3 a.m. The man, who Seattle police said was in his 30s, crashed his Eagle car into a barrier at the northern end of the tunnel.

The man was trapped and required extrication, and was ultimately pronounced dead at the scene.

Police said they believe speed was a factor in the crash. No further details were immediately provided.