Rescue teams at a South African mine are struggling to reach three missing workers who were buried in a mobile office container under thousands of tons of rock last week.

Australia-based Vantage Goldfields, which runs the Lily gold mine near Barberton town, said Wednesday that there were "some signs of life" during rescue operations Tuesday, a reference to tapping sounds apparently coming from the container.

The company says those sounds have not been heard so far on Wednesday. It says searchers are about 40 feet (12 meters) from the steel container and that time is running out for anyone to be rescued alive.

An underground pillar caved in at the mine Friday, creating a sinkhole that swallowed the container. All 87 miners who were underground during the collapse were rescued.