Update, 6:03 a.m.:

All lanes of the inner loop have reopened.

Original post:

A tractor-trailer overturned Monday night and forced authorities to shut down four lanes of the Capital Beltway in the New Carrolton area, authorities said.

The accident happened near the right shoulder of the inner loop, just north of Route 450, about 11 p.m., Maryland State Police officials said.

The man driving the semi was critically injured, said Mark Brady, a Prince George’s County fire department spokesman.

Authorities shut down four lanes, but were squeezing traffic by the accident along the left shoulder of the Beltway, police said.

The cause of the crash was not immediately known.

Clarence Williams is the night police reporter for The Washington Post and has spent the better part of 13 years standing next to crime scene tape, riding in police cars or waking officials in the middle of night to gather information about breaking news in and around Washington.