Douglas County Sheriff’s officers were trying to determine how a tractor-trailer rig wound up heading east in the westbound lanes of Kansas Highway 10 before a head-on collision early Tuesday.

The accident critically injured Joshua I. Walton, 20, a Kansas University sophomore, and his passenger, Ryan D. Galemore, 21, a former KU student now attending Johnson County Community College. Both are from Olathe.

Both men were taken by air ambulances to KU Med in Kansas City, Kan., Officials said Wednesday Galemore’s condition was upgraded from critical to serious condition. Walton remains in critical condition.

They had been in a 1998 Toyota Corolla.

The driver of the tractor-trailer, Horace A. Jordon, 51, Topeka, was taken by ambulance to Lawrence Memorial Hospital, where he was treated and released, a spokesman said.

The tractor trailer, a 2001 Freight Liner, is owned by Riverside Transport Inc., Riverside, Mo.

The accident occurred about 2 a.m. on the four-lane K-10, just west of the Eudora exit at Douglas County Road 1061, sheriff’s officers said. The westbound and eastbound lanes are separated by a grassy median.

From the time of the accident until 10:20 a.m., the westbound lanes were closed from County Road 1061 to East 1750 Road, a distance of about 4.5 miles, Undersheriff Bill Shepard said.

Shepard said he didn’t know how the truck got on the wrong side of the highway or how long it had been there before the crash. Neither could he say when the accident investigation would be completed. When it is done, a report will be sent to the Douglas County District Attorney’s Office for review, he said.

“It’s going to take awhile,” Shepard said. “There are a lot of things to look at.”

No one at Riverside Transport would comment about the accident.

“We’re still doing our investigation, and we can’t say anything yet,” said Brian Sodders, the firm’s safety manager.