Several of the 12 trapped miners who died in West Virginia left messages for their families to assure them they were not suffering in their final hours.

A relative said some wrote notes to say they were not in pain. "They said they weren't suffering, they were just going to sleep," said Peggy Cohen, whose father, Fred Ware, was among the dead. She said medical officials told her notes found on several bodies carried similar messages reading, "Your dad didn't suffer".

Some relatives are considering legal action against International Coal Group (ICG), which owns the Sago mine in Tallmansville. Amber Helms, whose father Terry died, said relatives would be probably pursue a lawsuit. "It's the biggest thing that's going to happen after these miners are put to rest," she told the NBC television network.

Mr Helms was the first victim found. His family did not have to endure the false euphoria others experienced after it was wrongly reported that 12 of the men were alive. A note was also left on Mr Helms' body, saying he had died peacefully. "We don't know who left the note," said his sister, Judy Shackleford.

State officials said post-mortem examinations would show what killed the men as well as when they died. How much of that information will be released is unclear.

Doctors say there was little change in the condition of the one survivor from the disaster, the worst of its kind in the US for four years. Randy McCoy, 26, remains in a coma, suffering a collapsed lung and dehydration.

The cause of Monday's explosion as well as how the incorrect information was relayed to relatives is being investigated. ICG has admitted relatives and friends were allowed to believe for hours that the men were alive although officials suspected that they were not. It has apologised.