Three rescuers attempting to find six workers trapped in a collapsed Utah mine in the US have been killed by another cave-in during rescue efforts, according to officials.

Tammy Kikuchi, spokeswoman for Utah's Department of Natural Resources, also confirmed that six rescuers were injured in the incident.

Hope had been renewed in the rescue efforts, after sound monitoring devices picked up noises - the first signs that the men may still be alive as no contact has been made with them since a mine tunnel collapsed on 6 August.

Yesterday's tragedy, which occurred at around 1.35am British time, will come as a blow to recovery efforts.

"Tonight we have witnessed a most unfortunate incident on top of last week's tragedy," Utah Governor Jon Huntsman said in a statement. "I hope the lessons we learn from this week in Utah will be instrumental in improving mine safety everywhere."

Rescue teams have been frantically trying to find signs that the miners are still alive, and three boreholes drilled into the mountain have allowed a video to be lowered, revealing an undamaged area.

Mine owner Bob Murray said the camera lowered into the borehole revealed areas of the mine completely undamaged by the collapse that trapped the miners.

In addition, each of six geophones placed around the mountain picked up sounds on Wednesday, and the vibrations were recorded in a steady pattern for up to five minutes.

However, experts have said that the chances of finding the miners alive are now slim, and as each hour passes that chance only gets smaller.

Murray previously praised the missing men's families, and he said they remained hopeful.

"They're holding up extremely well," Murray said. "Their strength is amazing, and I think it comes from their belief in their God."

The Salvation Army, meanwhile, has sent an Emergency Disaster Services (ESD) team from Salt Lake City to Huntington, where the mine is located, to assist the miners' families and emergency crews with food and drink refreshments as well as offering emotional and spiritual support.

The Salvation Army's ESD canteen vehicle has provided breakfast, lunch and dinner to around 100 people involved in the rescue effort each day since August 9, after called upon by scene officials who realised it was going to be a lengthier operation than originally hoped.