Update: 2:30 p.m. -- The California Highway Patrol reports that both northbound lanes on Highway 17 have been reopened. Because of the large traffic backup, officials say it likely will take some time for traffic flow to return to normal. In addition, southbound lanes have been affected with stop-and-go traffic from the Hamilton Avenue exit in Campbell to the Highway 9 exit.
Update: 12:59 p.m. -- The left northbound lane on Highway 17 has been reopened. Emergency responders are on the scene; traffic is backed up to Vine Hill Road.
An overturned truck has blocked both northbound lanes on Highway 17 in Los Gatos, just before the Redwood Estates turnoff.
Bay Area traffic website 511.org reports a severe traffic alert is in effect from the 12:22 p.m. incident. Motorists are advised to expect delays and to consider taking alternate routes.
Emergency responding vehicles are on the way to the scene; there is no estimated time for clearing the roadway.
Keep checking Patch for updates.
-- Bay City News contributed to this report