Huntington, Utah ? A disastrous cave-in Thursday night killed two rescue workers and injured at least seven others who were trying to tunnel through rubble to reach six trapped miners, authorities said. Mining officials were considering whether to suspend the rescue effort.

It was a shocking setback on the 11th day of the effort to find miners who have been confined at least 1,500 feet below ground at the Crandall Canyon mine. It’s unknown if the six are alive or dead.

Six of the injured rescuers were taken to Castleview Hospital in Price. One died there, one was airlifted to a Salt Lake City hospital, one was released and three were being treated, said Jeff Manley, the hospital’s chief executive officer.

The workers suffered injuries to the head and chest as well as cuts and scrapes, said Rich Kulczewski, spokesman for the U.S. Department of Labor. Two of the injured were federal mine safety workers, he said.

No official cause of death has been released for either fatality.

The second rescuer death occurred at Utah Valley Regional Medical Center in Provo. Another worker at the hospital was in critical condition with head trauma but was alert, said Janet Frank, hospital spokeswoman. Another worker was expected to arrive at the University of Utah hospital in Salt Lake City.

Officials said the cave-in was caused by a mountain bump, which commonly refers to pressure inside the mine that shoots coal from the walls with great force. Seismologists say such an event caused the Aug. 6 cave-in that trapped six men inside the central Utah mine. Thursday’s bump occurred about 5:30 p.m. CDT.

A mine employee, Donnie Leonard, said he was outside the mine when he heard a manager “yelling about a cave-in.”

A woman who answered the phone at the mine said mine co-owner Bob Murray, chief of Murray Energy Corp., was not available for comment.

It was not immediately clear where the rescuers were working or what they were doing when they were hurt. Crews have been drilling holes from the top of the mountain to try to find the miners while others were tunneling through a debris-filled entry to the mine.

Underground, the miners had advanced only 826 feet in nine days. Mining officials said conditions in the mine were treacherous, and they were frequently forced to halt digging because of seismic activity. A day after the initial collapse, the rescuers were pushed back 300 feet when a bump shook the mountain and filled the tunnel with rubble.

Before Thursday’s incident, workers still had about 1,200 feet to go to reach the area where they believe the trapped men had been working.

The digging had been set back Wednesday night, when a coal excavating machine was half buried by rubble by seismic shaking. Another mountain bump interrupted work briefly Thursday morning.

“The seismic activity underground has just been relentless. The mountain is still alive, the mountain is still moving and we cannot endanger the rescue workers as we drive toward these trapped miners,” Murray said earlier Thursday.

Murray had become more reticent to predict when the excavation would be complete. At the current rate, it was expected to take several more days.