Before they breached the tank car, crews were building dikes to channel the fluid and had material on hand to try to neutralize it.

Major roads were closed, including portions of the I-15 and I-80 freeways. It was expected that the freeways would reopen late Sunday.

An immediate mandatory evacuation was ordered Sunday afternoon from 600 West to West Temple and from 2300 South to 2700 South. Residents and business personnel were told to leave and stay away until the hazard had passed. The evacuation order was lifted at 10 p.m.

Other residents were advised to "shelter in place," in an area from 2700 South to 3300 South and from West Temple to State Street. If residents chose not to leave, they were asked to "stay in your house, turn off your ventilation system, and just stay in place until you're notified otherwise," said Capt. Tracy Tingey of the South Salt Lake Police Department.

As the day wore on, acid was melting larger holes in the tanker car.

"The problem's got worse by the hour," Foote said about 2 p.m. Officials worried about a tank rupture and an explosion.

"The actual holes are larger in size now," he said. "This is getting to be a very costly event, extremely costly."

Trying to gauge when the tank might rupture was difficult, he said.

The drama began about 6 a.m. Sunday, when workers noticed material leaking from small holes in the tank car. At first, officials suspected a saboteur may have shot the tanker, but then they realized that probably was not the case.

"Based upon information developed as a result of the FBI's Joint Terrorism Task Force investigation, it appears as though the cause of this incident is not terrorist or criminally related," said FBI Special Agent Bob Wright, speaking at the scene.

That was based on witness statements and assessments by hazardous materials experts as well as railroad personnel, he said.

"As a result, the FBI is scaling down its investigation and will be supporting other efforts being conducted by the safety and hazmat individuals and agencies."

Shortly before the attempt to drain the tanker, one of the crew tested its side, made of heavy stainless steel. The metal had been softened by the acid so badly that a ballpoint pen pushed through it easily.

About half an hour after the evacuation order, children were playing outside a home at 172 W. Oakland Ave. (2475 South).

Ramon Martinez, father of three of the children, said that was his parents' house, and relatives had gathered for a barbecue. At the time, about 10 children and five adults were present.

First to tell him of the evacuation order was a Deseret Morning News reporter.