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.