CARLSBAD, Calif. -- A big rig crashed off Interstate 5 and went down an embankment next to Batiquitos Lagoon Friday, dumping tons of asphalt and about 100 gallons of diesel fuel into the estuary, authorities reported.

The truck veered off the northbound side of the freeway and smashed through a guardrail while the driver was trying to exit at La Costa Avenue in Carlsbad shortly before 2 a.m., according to the California Highway Patrol.

The non-injury accident forced the closure of three of four northbound lanes for almost eight hours and caused rush-hour gridlock for miles, CHP public affairs Officer Larry Landeros said.

About 9:30 a.m., crews were able to open two of the affected lanes, and by 11:30 a.m. the damaged semi had been loaded onto a flatbed truck and hauled away, Landeros said. The far right-hand lane remained closed until about 2 p.m., the CHP reported.

The Highway Patrol notified state Fish and Game and county hazardous-materials officials about the pollution, which entered the lagoon about 100 yards from an open ocean outlet.