Salt Lake City ? A railcar leaking toxic chemicals sent plumes of gas into the air Sunday and forced the evacuation of more than 6,000 people for five hours. There were no injuries.

Fifteen hours after the leak was discovered Sunday morning, officials still were not certain of the contents of the leaking tanker, but they were pumping it into portable tanks and were letting people return to their homes.

The area downwind of the leak was evacuated because of fumes from the spill, Fire Chief Steve Foote said.

Officials were angered that they could not pin down what was in the tank and the information they were given conflicted with their own observations.

The manifest said it was sulfuric and hydrofluoric acids; the company told them it was hydrochloric, hydrofluoric, nitric and sulfuric acids. Late Sunday, the company corrected itself, saying the contents were phosphoric, acetic, sulfuric and hydrofluoric acids, and ammonia — all at a concentration of only 10 percent.

About 5,000 gallons had already spilled, but hazmat crews had not yet neutralized the spill, wishing to deal first with the tanker.

The tanker car originally carried 13,000 gallons of nitric acid at 94 percent concentration from Kennecott Utah Copper, a mining, smelting, and refining company, to Darwin, Nev., Foote said. He said the tanker car was then loaded with the industrial waste — whatever it was — and the train arrived at the Roper Rail Yard in South Salt Lake shortly after 6 a.m.

It was supposed to be taken to Ohio, where the waste was to be solidified and buried, but the tanker was found to be leaking.

Officials spent all day trying to find out from Phillips Environmental what the tanker contained.

“The rules are absolutely specific,” about detailing contents being shipped, Foote said. “Somebody dropped the ball here.”

Gov. Jon Huntsman said, “It’s tough to know how to respond if you don’t know the contents of the bulk container,” Huntsman said.

The leak got worse and the tanker wall began to soften. That prompted the evacuation about 5 p.m. Officials formed and changed plans as the condition of the tanker car changed.

Finally, specialized equipment arrived from Las Vegas that enabled crews to remotely pierce the tanker’s side and begin pumping the waste into portable tanks.

The evacuation order was lifted at 10 p.m., and officials expected to reopen the main Interstate 15 freeway within an hour or two.