A man has died and another has been seriously injured after being struck by a bulldozer and buried under tonnes of waste at a tip in Sydney's west.

The two workers were sorting waste material at the Eastern Creek facility when the accident occurred about 1.00pm.

According to Safe Work NSW, a bulldozer was being used to move waste when it accidentally hit the men.

"The machine pushed them into the waste material, making them very hard to locate," executive director Tony Williams said.

One of the men was able to be retrieved but the second was still buried under tonnes of rubbish when NSW Ambulance crews arrived.

"A frantic search then commenced by paramedics, police and fire brigades and also colleagues," NSW Ambulance Inspector Michael Magyary said.

"Probably 15 minutes after that we located the second person, he was found to be deceased."

The other man is in hospital with serious abdominal injuries.

Mr Williams said the driver of the bulldozer had undergone drug and alcohol testing and Safe Work inspectors had been on site to interview witnesses.

He said it would likely be "quite a complex investigation".

"But Safe Work want to reassure the community we will be having a very close look at the full circumstances around this incident …. to prevent further occurrences," Mr Williams said.

The facility is now closed but will likely re-open tomorrow with a non-disturbance order over the area where the incident occurred.

The Genesis Eastern Creek landfill site is the biggest in the southern hemisphere, with capacity of up to 2 million tonnes a year.

The 55-hectare waste management centre includes recycling and landfill facilities.

Operations opened at the Honeycomb Drive site in 2012. It was initially run by Dial A Dump Industries, which merged with BINGO Industries earlier this year.

In a statement issued tonight, BINGO Industries said they would be fully cooperating with authorities.

"This is a tragic event that has deeply affected our people," general manager Chris Gordon said.

"We intend to do whatever is required to understand how this incident has occurred to ensure that it never happens again."