Thousands of evacuees returned home Thursday after fire crews allowed a flaming propane rail tanker to burn itself out, ending the threat of a major explosion, authorities said.
Investigators turned their attention to finding the cause of the fire, which had threatened to engulf two other railroad tankers full of the volatile fuel.
Fire Chief Dave Whitt said the fire began Tuesday when an employee of Northern Energy opened an inspection port to measure the contents of a propane tanker parked on a railroad spur in the company's yard. Lincoln, home to about 42,000 people, is about 30 miles northeast of the state capitol.
Northern Energy ships in propane by rail, then unloads it into smaller tankers for truck deliveries to businesses and residences, Whitt said.
The port shouldn't have been pressurized, but it was, Whitt said, spraying the employee with propane that then ignited from a spark or static electricity.
"It engulfed him in flames," Whitt told The Associated Press. The man was treated for minor to moderate burns to his extremities.
The blazing tanker was surrounded by trucks, other rail cars and storage tanks containing at least 170,000 gallons of additional propane that Whitt said were at risk. A gas pipeline also runs through the area.
Whitt said crews were concerned a buildup of heat could lead to an explosion of the 29,000-gallon tank that could produce a fireball several hundred yards wide. An explosion also could throw metal shards up to a mile away.
Residents in nearly 5,000 homes within a mile of the tanker, a radius that includes much of the community and its entire downtown, were told to evacuate. They were allowed to return home around midnight.
"Yay, we get to go home," said 59-year-old Mary-Jane Coon, who fled along with her husband with just the clothes on their backs two days ago. "We're going home right now. My own bed, clean clothes."
Whitt's department will lead federal and state investigators in a probe of why and when the line was pressurized, and whether any valves, seals or other components failed. Whitt said there was no reason to believe it was anything other than an accident.
He estimated preliminary firefighting costs at more than $500,000, not including the economic cost of shutting down most of the city.
Northern Energy owns the product and the tanker car, said Federal Railroad Administration spokesman Rob Kulat.
A spokesman for Heritage Propane, owner of the Lincoln facility, did not immediately return a phone call.
Authorities allowed the blaze to burn after determining the car held less propane than previously thought. Fire crews initially planned to drain the propane from the burning car.
The fire burned out before midnight but was reignited to burn away any trapped vapors. Crews filled the car with water and a small amount of foam.
A similar fire in 1973 in Arizona killed 11 firefighters and a gas company worker when a rail car carrying a propane tank exploded. The resulting fireball injured more than 100 others and showered the area with shrapnel.
Residents who trickled back to their homes from evacuation centers questioned the proximity of the propane station to neighborhoods.
Carol Lopez, 43, who works at a head-start center, said she and other staff placed the children into evacuation strollers and reunited them with their parents.
"The fire department said you've got to get these babies out of here," Lopez said. "We left our purses, our driver's license, our IDs, everything is in there."
"It's just not OK to put something like this next to two schools," she added.
More than 6,000 students missed their first days of classes after the tanker caught fire. School officials said class would not begin until Monday.
Lopez said her 7-year old son was disappointed that school did not start this week. "He wanted to wear his new clothes, so we let him wear his new clothes anyway," she said.
Whitt said he expects a debate about the propane firm's location, but said the homes and the firm have been neighbors without incident for at least 25 years. The town grew up along the railroad, he pointed out, so derailments and other accidents also are ongoing hazards.
"It's not a matter of if we have a railway accident, but when," he said.
"It could have been a lot different," Whitt said. "We could be standing next to a crater."
Associated Press writer Judy Lin in Sacramento contributed to this report.