A partial ice cave collapse in unseasonably warm northwest Washington killed one person and injured four others Monday, a Snohomish County sheriff's spokeswoman said. Sheriff's spokeswoman Shari Ireton said late Monday night that the person who was killed remained buried under the debris at the popular Big Four Ice Caves east of Granite Falls. The recovery effort was suspended at nightfall.

All victims were believed accounted for, Ireton said. Three of the injured, including a 25-year-old man in critical condition, were airlifted to a Seattle trauma center. Also airlifted to Harborview Medical Center were a seriously injured 35-year-old man and a 35-year-old woman in satisfactory condition, hospital spokeswoman Susan Gregg said. Their injuries included cuts and leg and pelvis fractures, Gregg said. A fourth person, a juvenile girl with minor injuries, was sent to an Everett, Washington, hospital, Ireton said. Providence Regional Medical Center in Everett also expected a second patient, spokeswoman Diane Torrance said late Monday night.

The first call to emergency services came in about 5:38 p.m. Monday and the collapse probably happened about 45 minutes earlier, Ireton said. There was no cell phone service at the remote cave site.

The U.S. Forest Service warned hikers in May that the ice caves were in their "most dangerous state" due to unseasonably warm weather. The caves about 70 miles northeast of Seattle are a popular hiking destination in the Mt. Baker-Snoqualmie National Forest. Temperatures in the area Monday reportedly were in the 80s. On Sunday, a hiker filmed a section of the caves tumbling down. Several tourists were inside a cave during that collapse, but there were no reported injuries. The caves are formed by avalanches that cascade down from nearby Big Four Mountain during winter and spring. Most years, one or more caves form as the ice melts.