An off-duty Casper police officer died Wednesday night in a car accident north of Wheatland, Police Chief Tom Pagel said Thursday morning.

Alcohol is being investigated as a contributing factor in the crash, according to the Wyoming Highway Patrol.

Officer Kelly B. Pebbles, 39, was driving southbound in an F-250 pickup on Interstate 25 when the crash occurred at 4:59 p.m. Pebbles was 6.5 miles north of Wheatland when he tried to pass a tractor-trailer. His pickup struck the truck's front left corner and went off the highway in a broadside slide, the highway patrol said.

His truck hit a tree and Pebbles, who was not wearing a seat belt, was ejected from the truck. He was pronounced dead at 6 p.m. at Platte County Memorial Hospital in Wheatland.

The Wyoming Highway Patrol received a suspected impaired driver report on Pebbles' truck minutes before the crash, said Sgt. Stephen Townsend of the highway patrol. The report was relayed through the Platte County Sheriff's Office at 4:56 p.m

The caller said the pickup was northbound in the southbound lanes and almost hit a guard rail. A highway patrol officer was dispatched but didn't reach Pebbles' vehicle before the crash.

The Wyoming Highway Patrol is investigating the accident. Townsend didn't know the speed of the truck at the time of the accident.

The road was dry at the time, he said.

It was the 12th fatality of 2007 on Wyoming roads.

Pebbles was divorced and had no children, Pagel said. He was born and raised in Casper - where his mother, sister and brother still live -- and had been with the Casper Police Department since 2001.

In 2005, he was commended for intervening in a medical situation where a person might have otherwise died. A year earlier, he received a life-saving medal for saving a heart attack victim's life, according to Star-Tribune archives.

Pebbles previously worked as an emergency medical technician for Wyoming Medical Center, according to archives. While working as a paramedic in 1995, he received a letter of appreciation for his effort during an apartment fire. Off-duty at the time, Pebbles helped the Casper Fire Department with fire hoses, aided in carrying a victim to safety and assisted with first aid.

In Wednesday's crash, the driver of the tractor-trailer was issued a citation for exceeding hours of service for operation of a commercial vehicle.

Cory A. King, 32, of Windsor, Colo., was driving a 2004 tractor-trailer for United Food Service. He was wearing a seat belt, as was his passenger, Anthony Duran, 44, of Westminster, Colo.

King was able to steer his truck to a stop in the emergency lane and neither man was injured.

Reach Joshua Wolfson at (307) 266-0582 or josh.wolfson@casperstartribune.net.