CLIFTON, N.J.—Officials say a U.S. man jumped into a vat of acid to save a co-worker who had fallen in.

Rob Nuckols jumped in Monday when colleague Martin Davis fell through a roof and into the vat of acid, becoming fully submerged.

Nuckols was waist-high while he and others pulled Davis out, Fire Chief Vince Colavitti told The Record of Woodland Park in New Jersey. The acid was used for cleaning metal tubing.

Rescue workers cut Davis out of his clothes and sprayed him with water to limit burns. A relative says Davis is in critical condition.

Nuckols was treated for burns on his legs and abdomen.

An employee at Swepco Tube LLC says the company had no comment.