Two people were rescued from a Northern California mountain in critical condition Monday and a third person died amid “tough” conditions, authorities and a witness said.

The incident involving the fatally injured victim, who wasn’t identified, was reported early Monday on Mount Shasta, near the Oregon border, the Siskiyou County Sheriff’s Office said.

The person was confirmed dead before a rescue effort was launched, the sheriff’s office said.

Another person injured in the incident was in critical condition, the sheriff’s office said. A third person suffered a broken ankle.

A fourth person was in critical condition after a second incident on the mountain Monday afternoon, the sheriff’s office said.

A California Highway Patrol helicopter crew rescued a fifth person Monday night who earlier had been reported missing and injured. Her condition wasn’t immediately available.

The sheriff’s office didn’t say what caused the injuries or the death. It described the people as “climbers.”

At more than 14,000 feet, Mount Shasta is a popular climbing destination during the spring and early summer.

In a video posted by the sheriff’s office, Wallace Casper, of Bozeman, Montana, described the treacherous environment on the mountain Monday, saying a layer of “water ice” atop the snowpack made it impossible to navigate on skis.

“A lot of people had issues with falling and sliding,” he said.