A New Jersey roofer jumped into a vat of nitric acid solution to save a co-worker who had fallen 40 feet into the tank, fire officials said.

Rob Nuckols, 51, was working on the ground floor on Monday morning at Swepco Tube LLC when his colleague Martin Davis plunged through a roof and into the vat of diluted acid and became fully submerged, officials said.

He jumped into the vat and was waist-high while he and three others pulled Mr Davis out, Clifton Fire Chief Vince Colavitti told The Record of Woodland Park. The vat contained a 40 to 70 per cent nitric acid solution used for cleaning metal tubing.

Rescue workers arrived after five minutes, cut Mr Davis out of his clothes and sprayed him with water to limit burns, Mr Colavitti said. Mr Nuckols had already rinsed himself off.

Mr Davis is in critical condition with a broken rib, punctured lung, and burns on his legs and side, a relative said.

Mr Nuckols was treated for burns on his legs and abdomen. The three other roofers were taken to hospitals but there was no sign that they were seriously injured.

The men were working for Gar Con Enterprises of Flemington. The federal Occupational Safety and Health Administration said it was investigating and looking into both companies.

An employee at Swepco said the company had no comment, and Gar Con did not return calls.