EUGENE, Ore. -- Investigators were looking for clues Thursday into what sparked a series of grass fires that closed down Interstate-5 near Eugene Wednesday afternoon.

The fires created chaos for drivers and sending one man leaping out of his hay truck after it went up in flames.

Photo from kgw.com viewer Jess Kenoyer

The driver of the hay truck leaps out of the cab to save himself.

Jess Kenoyer was driving behind the double-trailer hay truck and snapping photos of the fire when the truck driver pulled over and suddenly jumped out of the cab to save himself and it was captured on camera.

Authorities said the truck driver was not injured. They believe flaming debris ignited the hay on his trailers.

About 46 units from various agencies responded. "We've got a countywide deployment of resources," said Elaine Parrott, a spokeswoman for the Jefferson Fire District.

By early Wednesday evening the smaller fires along northbound I-5 were out and crews concentrated on the larger one near Santiam Bluff.

As firefighters responded, authorities initially closed all lanes of  I-5 at milepost 238 and traffic was being detoured through Jefferson. The roadway was eventually re-opened late Wednesday night.

 Slideshow: Viewer photos of hay truck fire and grass fires

The other grass fires were scattered along a 50-miles stretch between Eugene and Jefferson, with the largest located on the south side of Santiam Bluff near the Mitchell Rock Quarry where "trees, grass, and brush are currently burning but no structures are threatened," said Elaine Parrot with the Jefferson Fire District.

Investigators on the scene were unsure exactly what caused the sudden grass fires, but speculated that vehicles with mechanical problems or with metal scraping the roadway may have created sparks that ignited in the dry grass and brush lining the interstate.

Drivers were advised to avoid the area if possible or expect long delays even after the roads were re-opened. Traffic had backed up so far that the Willamette River bridges, Salem Parkway and Mission Street were even jammed in the Salem area.

 Traffic updates: Check road closures | Map of grass fires

"If drivers see smoke across the highway or emergency vehicles, be prepared to slow down and change lanes to give fire crews room to maneuver," warned ODOT District Manager Mike Spaeth.

Anyone with information was asked to call Oregon State Police.

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