Monday's collapse came after authorities warned that the caves were especially dangerous because of warming temperatures.
The person who died remained buried under the debris at the Big Four Ice Caves east of Verlot, Snohomish County sheriff's spokeswoman Shari Ireton said late Monday night. 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. They included 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.
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 ice caves have been closed until further notice.
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. Temperatures in the area Monday reportedly were in the 80s.
Multiple warning signs have been put up in the past year to indicate the danger, Tracy O'Toole, a spokeswoman for the Mount Baker-Snoqualmie National Forest, told the Daily Herald of Everett.
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.
In July 2010, an 11-year-old girl was killed near the caves by a bouncing chunk of ice. She never even went inside the caves.
Chloe Jakubowski, 18, told The Seattle Times that she and three friends drove about 15 miles to a pay phone to alert emergency crews to the injuries.
"Everybody there, we grabbed everybody out and helped as best we could," she said.
Jakubowski told The Times she and a handful of others were in the cave when she heard a loud crack, then ice and debris cascaded down. She said she covered her head with her arms and crouched behind a giant rock of ice.
When she stood up, a woman next to her lay unconscious. Others nearby had cuts and broken bones.
"It was extremely gruesome, honestly," said Jakubowski, who suffered scratches and other minor injuries. She said she saw the warning signs outside but went in anyway, adding she didn't see anything that seemed to point toward a collapse, and others already were in the cave.