The risk of an explosion or spill has fallen significantly, the authorities said late Tuesday, and all evacuated residents can now go home. Some have begun to ask who should be held accountable.

By Shawn Hubler and Rebecca Fairley Raney, The New York Times

Southern California officials lifted a sweeping evacuation order in Orange County late Tuesday after firefighters announced they had stabilized a damaged chemical tank that had posed a risk of a potentially catastrophic explosion or spill.

Over Memorial Day weekend, fears about a compromised tank at an aerospace facility in Garden Grove, Calif., forced nearly 50,000 residents from their homes and prompted state and federal emergency declarations.

More than 30,000 people were allowed to return on Monday night, after firefighters managed to cool down the tank’s toxic contents. However, the remaining 16,000 or so residents who lived closer to the tank had been told to stay away until firefighters could be sure the chemicals were truly stable. That determination came Tuesday evening.

Residents had to evacuate late last week after firefighters determined that a pressurized container containing a toxic substance had overheated and was poised to burst at GKN Aerospace’s manufacturing plant in Orange County. GKN, which is based in Britain, produces components for military and civilian aircraft.

The crisis, which officials had feared would end either in a toxic blast or a devastating hazardous waste spill, drew worldwide attention.

Emergency responders and scientific experts raced to cool down the bulging tank and safeguard surrounding communities. They doused the tank for days with water sprayed from fire hoses and opened more than half a dozen evacuation sites in a matter of hours on a holiday weekend.

By Monday, firefighters reported that the tank’s temperature had begun to drop and that it was safe for most evacuees to begin returning.

On Tuesday, Greg Barta, an Orange County Fire Authority spokesman, reported that the temperature inside the tank, previously in the triple digits, had dropped to about 92 degrees and was holding steady. As the day progressed, fire officials said, they ceased dousing the tanks.

On Tuesday evening, after a four-hour period during which the tanks remained stable even without the cooling measures, fire officials lifted the evacuation order for all residents, some of whom had been sleeping in cars or tents since Friday. Officials reduced the restricted area to a 300-foot perimeter around the equipment.

Apologizing for interrupting the meeting, Mr. Covey told residents, “I didn’t want to delay your getting home.”

The incident has prompted members of the communities around the plant to demand accountability from GKN and the local authorities.

“The imminent threat has been taken out of the equation, but this raises serious questions about the extent to which the government allowed this facility to expand,” said Carlos Perea, executive director of the Harbor Institute for Immigrant & Economic Justice, one of several local organizations that called for the relocation of GKN Aerospace from Garden Grove, where it has operated for decades.

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