Workers rushed to save crushed colleagues

Two male workers were crushed to death and another seriously injured after tonnes of truck-building materials collapsed on them in a shipping container in Sydney's west.

The three men were working inside the container at the Westrucks industrial yard at Wetherill Park when they were struck by falling timber and fibreglass panels on Thursday morning.

Nearby work mates rushed to their aid, trying to lift the giant slabs off them.

"Those things weigh enormous amounts," said Inspector Kernin Lambert, from NSW Fire and Rescue.

"They placed their own lives at risks to try and save the two workers who were trapped."

Emergency services arrived just after 11am where they stabilised the load but were unable to save the two men.

On Thursday afternoon authorities were still working to retrieve their bodies.

The third worker managed to pull himself free and was taken to Fairfield Hospital in a serious condition.

Both the police and WorkCover NSW are investigating.