UPDATE: 6:50 a.m. A second big-rig has overturned on I-580 this morning, this time in the eastbound direction near the Altamont in Livermore, according to news reports.
A report on KTVU says a double tractor trailer overturned after the driver said he began fishtailing in heavy rain. The crash is blocking three lanes.
From Bay City News as of 6 a.m.:
All lanes have reopened on westbound Interstate Highway 580 in Pleasanton after a big rig overturned earlier this morning, according to the California Highway Patrol.
The collision, located near the connector ramp with northbound Interstate Highway 680, was reported at 1:51 a.m. and blocked traffic until about 6 a.m., according to the CHP.
According to the CHP, the big rig spilled oil and diesel fuel onto the pavement during the collision.
A Sigalert had been issued for the area.
Patch will update this story as we get more information.