May 12 (UPI) — Three rock climbers were killed over the weekend in a climbing accident in the North Cascade mountains in Washington state, as investigators look into equipment failure.

“A party of four climbers from Renton, Wash., were involved in a fall while descending a steep gully, ” according to a statement Monday from the Okanogan County Sheriff’s Office.

“The presumed cause of the accident is anchor failure while rappelling, with more investigation still ongoing,” the sheriff’s office added.

The four men, who have not been identified, fell nearly 200 feet at around 11:30 a.m. PDT, on Sunday, in the area of North Early Winters Spire off of State Route 20 in the North Cascades.

Three of the climbers, ages 36, 47 and 63, were pronounced dead at the site of the fall. The fourth member of the group survived and hiked back to a car, before driving 60 miles to find a pay phone and call for help.

“There was a long time delay before he got to Newhalem,” said Undersheriff David Yarnell of the Okanogan County Sheriff’s Office.

The climber was taken to Harborview Medical Center in Seattle, where his condition is unknown. According to Yarnell, he walked out not knowing “he had as significant of internal injuries as he did.”

Yarnell blamed equipment failure for the fall, saying that all four climbers were tied to the same anchor point, which is “not preferred.”

“Investigators will try to determine whether the climbers were using a pre-existing anchor point, or their own gear … All we know is that the anchor point that they were all tied off to failed,” he said.

The Snohomish County Helicopter Rescue Team was able to retrieve the remains of the three climbers killed in the “technical, mountainous terrain.”

“Our thoughts are with the family members and friends of those involved.”