A large sinkhole closed a long southbound stretch of the George Washington Memorial Parkway in Fairfax and Arlington counties Monday night, and officials said the closure could last into the morning rush hour.

The parkway was closed between Route 123 and Spout Run Parkway, said Sgt. Lelani Woods of the U.S. Park Police. The distance is about four miles.

Southbound traffic is being diverted onto Route 123, and the ramp from 123 onto the southbound lanes of the parkway will remain closed until further notice, she said.

Northbound lanes remain open, and the southbound lanes are open south of Spout Run, she said.

The sinkhole was spotted some time after 10 p.m., Woods said. Preliminary reports did not indicate that it caused any damage to automobiles.

One alert described the sinkhole as about 30 feet by 20 feet. Its depth could not be learned immediately.

The cause of the sinkhole was not immediately known, and it was not clear if rain was a factor.