Questions hang like an orange acidic haze over Sunday's incident in which a 13,000-gallon rail tanker car leaked toxic material.

Officials and company spokesmen have not agreed on some basic facts. But answers to those questions could help place responsibility for the incident, which forced the evacuation of about 8,000 South Salt Lake residents and closed freeways and roads.

• Kennecott, which owns the rail car, says it bore the logo "sulfuric acid." Did that mean it should have carried only sulfuric acid rather than the mixture that was inside?

• Was it a chemical reaction, mechanical failure or both that caused the leak?

• The manifest listed more than one type of acid and "inorganic" material, and carried the notation "mixed acids." Should that have tipped off company officials or regulators that trouble was brewing?

• Should ammonia have been in the car? Should it and other material have been specified on the manifest?

• The tanker was leased by Philip Services Corp. or PSC, a hazardous waste shipment company based in Houston. Did Kennecott receive the manifest on March 1, the date PSC says it was faxed to the Utah company? If so, did Kennecott have any responsibility in the matter?

• Why was the car in South Salt Lake when PSC says it was supposed to roll directly from Nevada to a disposal site in Ohio?

Some of the answers may come from the Federal Railroad Administration, which has launched an investigation.

An estimated 6,000 gallons of liquid spilled after the tanker was discovered leaking early Sunday in Union Pacific's Roper Yard, 2270 S. 600 West, said Teresa Gray, supervisor of water quality and hazardous waste for the Salt Lake Valley Health Department. The remainder was pumped out.

The Utah Department of Health laboratory at Research Park analyzed the material and determined these contents, she said: hydrofluoric acid, about 6 percent; nitric acid, 1 percent; sulfuric acid, 6 percent; acetic acid, 1 percent; hydrochloric acid, 2 percent; ammonia, 2 percent; phosphoric acid, 0.5 percent. The rest was water.

"They're very toxic," Gray said of the chemicals. Vapor can get into the lungs and damage the eyes and skin, she said. "We have had no reports of injuries because of this," she added.

South Salt Lake Fire Chief Steve Foote said nitric acid should have been specified on the manifest. Even if it was present only in small concentrations, his department should have been informed immediately that it was there, he said.

It's not enough to list a couple of materials and then combine the rest of the contents into some generic label, Foote said.