Bracken, who visited the rig last week after unions won the right to access the workplace, said the drill on the 36-year old semi-submersible rig had jammed.

Peter Meddens from Darwin and Barry Denholm from Lossiemouth in Scotland were killed in the August 27 accident.

Bracken said the crew on the Sunday night before the accident occurred had refused to conduct the work because they felt it was unsafe.

"The drill had been stuck in the hole for five days," he said.

"They informed the guys on the day shift [that they felt the work was too dangerous]."

Despite this, the work continued the following morning.

Bracken said the MUA members on the rig had been involved in providing first aid to the men.

A National Offshore Petroleum Safety and Environmental Management Authority spokeswoman said the authority would not comment on the incident until after its investigation was completed.

Stena Drilling is working for Origin Energy on a six-well drilling campaign in VIC/P43 in the Otway basin about 90 kilometres south of Warnambool.