WARSAW, Ind. (AP) _ An iron furnace blew up at a foundry Thursday and hurled 2,600-degree molten metal at workers ``like a shotgun blast,'' burning off clothing and flesh. Nineteen people were injured, four critically.

William Slone, an employee, was 50 feet away when the furnace exploded at Dalton Foundries Inc. at about 2:45 a.m. He saw three of the worst injured as they fled.

``When they came out the door, their skin was hanging off, their clothes were burned off, some looked like they had teeth knocked out,'' Slone said. ``One of them, all that was left was the collar from his shirt, and he was burned from the knees down.''

Investigators said that a small explosion caused by moisture in the furnace ruptured a water line, dousing the molten metal with a larger amount of water and triggering a much larger blast.

``It's a liquid metal,'' said Fire Chief Ken Shepherd, whose crews put out the flames with chemicals and sand. ``Putting water on it is like putting dynamite on it. The water is more of a hazard than the metal.''

Four workers were listed in critical condition, one was serious, and two were fair at the burn unit at St. Joseph Medical Center in Fort Wayne, about 40 miles to the east. The remaining patients were treated and released.

Paramedic Chris Fancil said he treated a man with second-degree burns over 90 percent of his body.

``His pants had actually burned through,'' he said. ``They were crisp. ... They were pretty well melted. They were jeans, and they became almost like paper. He had skin hanging from every part of his body.''

State records show the foundry has been cited for 29 safety violations and fined $10,425 since 1982, when the Indiana Occupational Safety and Health Administration began keeping computerized records. There was one death since then.

But Ken Haselwander, a spokesman for the state agency, said the foundry is ``maybe a little better than average'' about safety compared to similar-sized companies.

The largest single fine against Dalton was $8,000 last year for 14 separate violations. Three were listed as serious, including failures to have a machine guard on a drill press and a procedure for disabling a machine during maintenance. There were no violations on record involving accidents similar to Thursday's.

The workers ``were peppered like a shotgun blast'' by chunks of melted metal, said Slone, who was knocked down and burned on the arm. He said the iron was about 2,600 degrees.

``It was just a large explosion, like a very large amount of TNT,'' he said.

About 150 to 200 people were on duty at the time.

``It's one of the unfortunate things with an accident like this, there's no warning whatsoever,'' said plant security chief Bob Robinson. ``Just, boom, then it's all over.''

The 85-year-old foundry, which covers about four city blocks, makes iron castings from scrap metal. With 700 employees, it produces large compressor housings for refrigeration equipment and parts for utility pipelines.

Dalton President Ken Davidson said damage was largely confined to one furnace and production will resume Sunday night.