A gasoline tanker overturned on U.S. Highway 101 in San Jose Thursday morning, blocking traffic for hours, authorities said.

The California Highway Patrol said the tanker collided with a pickup truck that had slowed down on southbound 101 at Hellyer Avenue because of flooding on the roadway at about 10:45 a.m. 

The driver of the smaller truck was not injured, but the tanker's driver was taken to the hospital to assess injuries. The crash closed all southbound lanes as hazardous materials crews worked to clean up over 600 tons of gas, the CHP said. 

The estimated reopening time is 5:00 p.m. An alternative route for southbound 101 travelers was Monterey Road to Highway 87 to  Highway 85.  

Portions of major Highway 87 and Highway 85 in San Jose were also closed due to flooding.