Investigators say the Ironman Boulder competitor who was struck and killed by a vehicle during the cycling portion of Sunday’s triathlon was out of the designated race lane on her bicycle before she was hit.

Michelle Walters, 34, of McCook, Neb., died after being hit at the 31.9 milemarker of U.S. 36 at 9:47 a.m. Sunday just north of Boulder, according to Colorado State Patrol Trooper Nate Reid.

Reid said Walters was in the coned-off race lane on westbound U.S. 36 — which at that section of the road heads north out of Boulder — ahead of a Toyota Tacoma pickup truck also headed north.

For some reason, Walters veered out of the designated race lane and into the lane designated for vehicle traffic. The right side of the pickup truck hit Walters’ left side, causing her to fall off her bike and be struck by the truck.

She was taken to Boulder Community Health’s Foothills Hospital, where she died, according to Reid.

The driver of the truck, identified as Timothy Lacey, 55, of Boulder, was not injured. Lacey stayed on scene and cooperated with investigators after the crash.

Officials said alcohol and speed are not believed to be contributing factors in the crash, and no citations have been issued at this time.

Reid said it is not clear why Walters veered from the designated race lane. The crash is still under investigation.

U.S. 36 north of Boulder had not been closed to vehicle traffic during Sunday’s race. That stretch of the two-lane road had a shoulder blocked off with cones for cyclists and traffic realigned for the race, which Ironman Boulder race director Dave Christen said has been the case for the two previous races in Boulder.

“Those are conversations we have internally with Colorado State Patrol,” Christen said. “We do put a lot of thought and process into what we think is safe and proven safe. It’s something we’ve been planning for months on end.”

Reid said while closing an entire highway would be safer, it would severely affect traffic in and out of Boulder.

“They come up with a plan, and based on that we decide how many troopers are needed to staff the event,” Reid said. “Ultimately, we approve their plan. The expertise lies with the organizer. They do these types of things all over the country. Obviously, we have to balance the community’s needs and the safety of the participants at the same time.”

Members of Walters’ family declined to comment when reached on Monday.

A group called The Greater Omaha Area Trail Runners (G.O.A.T.z) posted on its Facebook page about Walters, saying she had run one of their races in June.

“G.O.A.T.z is often times referred to as a ‘family,’ a community of runners whose well-being and success is shared jointly regardless of your location on the map, or how many G.O.A.T.z races you’ve run,” the post read. “Once you’ve joined us, you’ve become a part of the family. Michelle became a part of our family last June. Our thoughts and prayers are with Michelle’s family during this sad and trying time.”

Christen could not say if it was Walters’ first Ironman.

He added: “Our thoughts are with the family. We are working with state patrol to gather as much information as we can.”

The crash marks the fourth time a cyclist has been killed by a driver in Boulder County since late May. It is also the second year in a row an Ironman Boulder competitor has died.

Brian Godlove, a competitor from Virginia, was taken to the hospital from the race course after completing the swim and cycling portions, but not the final running leg. He died three days later at Boulder Community Health.

The Boulder County coroner ruled he died from dehydration and rhabdomyolysis associated with excessive exercise.

Between 2003 and 2011, there were 43 race-related deaths at various Ironman events sanctioned by USA Triathlon, the sport’s national governing body.

Five of those 43 deaths were caused by traumatic injuries sustained in cycling crashes. Beyond that, 30 deaths occurred during the swim portion of the race, three during the bike leg, three during the run and two after an athlete had finished the race.

The Denver Post contributed to this article.

Mitchell Byars: 303-473-1329, byarsm@dailycamera.com or twitter.com/mitchellbyars