Man dies, another critical after falling into an ink tank in Sydney workplace incident

A man has died after becoming trapped in what is believed to be an ink tank at a factory in Sydney's west.

A rescue operation was launched at an Auburn work site about 8.45am on Thursday following reports three men had been injured.

Two workmates were extricated from the tank at the ink factory and transported to Westmead Hospital, but the third man, believed to be in his 30s or 40s, died at the scene, a NSW Ambulance spokesman said.

"This is a terrible tragedy," NSW Ambulance Superintendent Paul Turner said in a statement, adding they had deployed 10 resources to try and help the stricken men.

"We did absolutely everything we could.

"It was a complex operation. We worked as quickly as we could to access these patients."

The man is yet to be formally identified and his body remains in the tank, a NSW Police spokesman told AAP.

Detectives have established a crime scene and are investigating.

SafeWork NSW has also sent inspectors to the site to investigate, a spokesman told AAP.

Phones in the factory's office have gone unanswered and the out-of-hours manager declined to speak with AAP.

A NSW Ambulance spokesman earlier said the extraction operation was expected to take several hours.

"It is understood that the rescue will be a complex operation and may take four or more hours," the spokesman said in the earlier statement.

Paramedics, NSW Fire & Rescue and Police Rescue all attended the scene at Chisolm Road.

One of the men rescued was transported to Westmead Hospital with leg fractures and another with leg injuries.