Despite numerous tips, the State Patrol is still seeking the vehicle that leaked the slick fluid that caused as many as 40 traffic accidents Wednesday night on Interstate 5 between Tacoma and downtown Seattle.

Troopers say the vehicle is probably large, possibly a semi-truck. They traced the fluid spill on both sides of I-5 from the Mercer Street exit in Seattle to the Flying J Travel Plaza, a truck stop near the Port of Tacoma, Trooper Kelly Spangler said.

Troopers say the vehicle may have traveled north on I-5 from Tacoma to the Mercer exit, then driven around downtown Seattle and returned south to the Flying J. Spangler said the amount of fluid found on the roadway led authorities to believe it was from a large vehicle.

Dawn Ramsey, facilities manager of the Flying J, said no spills or leaks occurred at the business Wednesday or yesterday. "We record all of those types of things," Ramsey said.

As of yesterday evening, the State Patrol had received nine tips on the source of the spill, but Spangler said none had turned up anything concrete.

"The odds are against us" because it was dark and hard to see a fluid leak, Spangler said. The fluid sent vehicles sliding out of control on both sides of the freeway. None of the accidents resulted in serious injury.

State Department of Transportation crews briefly closed the northbound Mercer exit and spread sand on the roadway to soak up the fluid. Spangler yesterday could not confirm previous reports that the slick substance was hydraulic fluid.

The driver of the vehicle could face a citation for the use of defective equipment, Spangler said. The driver or owner of the vehicle also could potentially be liable for damages in the 40 collisions.

Spangler asked anyone with information to call the State Patrol at 425-649-4370.

Nick Martin: 206-464-3896