An avalanche has forced the closure of Richardson Highway for at least a week north of Thompson Pass, the city of Valdez, Alaska, said Monday. The city released a statement Monday saying the Richardson Highway between Valdez's Mile 12 and Mile 64 will remain closed "for at least one week, but very possibly longer" while cleanup crews work to clear the snow from the avalanche caused by a snow dam at Keystone Canyon, the Anchorage Daily News reported Monday. The Alaska Department of Transportation, which said Sunday the road could be cleared as early as Tuesday, amended its estimate Monday to say the road will be "closed until further notice." "The crews were successful in bringing down several additional slides and have started removing slide debris on some parts of the highway," the department said Monday. "One of the larger slides in Keystone Canyon crossed the Lowe River and has formed a dam which, in turn, is flooding the valley upstream. These waters are receding, but at this time it is still far too dangerous for our crews to begin clearing this section of road." Valdez said its airport and port remain in operation and officials are working to increase ferry traffic to and from Whittier for the duration of the cleanup efforts. "The city of Valdez has confirmed that there is plenty of gasoline and heating fuel oil in town to serve local needs during an extended road closure," the statement said. "Should fuel run short at any time, it will be barged in as needed."