One man is dead and two others are in hospital after an industrial accident left them trapped inside an ink vat at a manufacturing business in Sydney's west.

Michael Stinson, a worker on site, told the ABC that two men rushed to help the third when he became trapped in the vat while conducting maintenance.

New South Wales Ambulance were called to the business, DIC Australia, at 8:45am.

New South Wales Fire and Rescue said the men, believed to be aged in their 30s or 40s, were "trapped by compression" at the site on Chisholm Road in Auburn.

The tank or vat was a cylinder shape and several metres high, Western Sydney NSW Ambulance Superintendent Paul Turner said.

"It is my belief that the arm inside the vat has caused the men to become trapped," he said.

It is understood the men were performing maintenance when the incident happened. ( AAP: Peter Rae )

"My understanding is that the men were doing maintenance … inside the vat but there was still ink hampering rescue efforts."

Two men were freed from the accident site and taken to Westmead Hospital with leg injuries and fractures, while the third man died inside the tank.

NSW Police and WorkSafe NSW will be investigating. ( ABC News: Richard Hoskins )

"The last person deteriorated on the scene … multiple ambulance resources [were] inside with the man trying to save his life," Superintendent Turner said.

"[The accident is] very tragic three weeks out from Christmas."

DIC Australia's website said the company produced inks for magazines, packaging and other printing products as well as metal decoration for foods and drinks.

NSW Police and WorkSafe NSW will be investigating the incident.

The man's body has been removed from the ink vat.

The two men taken to hospital are in a stable condition.