One driver was injured and another killed in two separate southwestern Riverside County traffic collisions that snarled traffic Monday.

A three-vehicle chain-reaction collision backed up traffic on Interstate 15 in Temecula and Murrieta for about two hours. Saul Ayala, a 22-year-old Temecula man, suffered minor injuries during that accident and was treated at nearby Rancho Springs Medical Center.

In Wildomar, the driver of a Norco paint store's pickup was not so lucky.

According to a California Highway Patrol report, the victim, a Corona man, whose name was not released, was headed south on Mission Trail when he lost control of his pickup and smashed head-on into a northbound beer-delivery truck at about 11:15 a.m. Monday.

How the driver lost control of the truck was not clear Monday afternoon, authorities said.

That traffic death was the 11th since Jan. 1 on stretches of road patrolled by the officers assigned to the Temecula CHP office. The Temecula patrol area, which includes northern San Diego County and stretches through Lake Elsinore, averages about 50 fatalities in a year.

CHP Officer Ron Thatcher said the driver of the delivery truck, Barry Ring of Menifee, told investigators he was slowing his empty truck to turn onto Bundy Canyon Road when the noticed the pickup drifting toward him. Ring told Thatcher that he could see the young driver of the paint truck clearly and that he had his head down and eyes shut.

"There was no braking, no evasive turning" by the paint truck, indicating the driver may have already passed out when he hit the beer truck, Thatcher said.

An autopsy and toxicology test will be performed to figure out what happened to the driver. Thatcher added the paint truck driver's boss said he had no idea why that truck would have been in the area Monday morning.

The impact of the collision smashed in the whole engine compartment of the paint truck and tore off the front left tire, the axle it was attached to and part of the beer truck cab. While shaken up, Ring was not physically hurt in the wreck.

Mission Trail was closed between Bundy Canyon and Canyon Drive until mid-afternoon Monday, causing drivers to find a different route to their destinations but no real traffic problems.

Traffic was backed up but not detoured after the 11:55 a.m. chain-reaction collision of three southbound vehicles on I-15 between Murrieta Hot Springs and Winchester roads.

The driver of a large truck, 44-year-old Adan Pimentel of Riverside, briefly took his eyes off the road ahead and did not notice that traffic had slowed, Thatcher said. Pimentel's 1996 Mack truck struck Ayala's vehicle, a 1986 Ford van, and then overturned.

The van then collided with a 1998 Oldsmobile driven by Beatrice Armas of Sun City. Neither Pimentel nor Armas was hurt in the accident, Thatcher said. The Mack truck blocked two lanes of traffic, but two others remained opened, and cars slowed and inched past until the vehicles and debris were cleared from the freeway.

Thatcher said he did not know whether Pimentel would be cited for his inattention.

Thomas Buckley can be by e-mail at tbuckley@pe.com or by phone at (909) 245-2934. Tim O'Leary can be reached by e-mail at toleary@pe.com or by phone at (909) 587-3133.