Federal agents on Wednesday were searching the premises of an aerospace company in Orange County, Calif., where last month tens of thousands of people fled their homes after officials said a chemical tank was at risk of exploding.

Agents from the F.B.I. and the E.P.A. were collecting evidence including records that might show who was involved in the storage of the hazardous chemicals; samples of the substance within any “tank, tote, drum, vat, vessel or container”; records of equipment inspections; and digital devices, among many other items, according to a warrant authorities obtained last week.

A spokesman for the U.S. attorney’s office in Los Angeles confirmed that agents were searching the site on Wednesday morning.

The evidence was collected at an industrial site belonging to GKN Aerospace, whose tank was the source of the near disaster. It contained 7,000 gallons of methyl methacrylate, which had become pressurized and was overheating as it released gas. The tank, officials had said, was at risk of exploding into a massive fireball.

As temperatures increased in the tank, officials became alarmed and issued evacuation orders for more than 40,000 residents on Friday, May 22, sending them into shelters for the Memorial Day weekend. Firefighters cooled the tank by spraying water at its exterior.

By that Monday, officials said that the worst-case scenario had been averted, because the tank had cracked, which had relieved the pressure. Evacuation orders were rescinded for more than half of the residents who had to flee their homes, although some who lived near the site had to wait longer to return home.

Both Gov. Gavin Newsom of California and the White House had issued emergency declarations as the crisis unfolded.

On Wednesday, television stations were showing helicopter footage of agents on the premises.

GKN Aerospace issued a statement saying, “we are cooperating with authorities at our Garden Grove facility and will continue to do so.”

The company, based in Birmingham, England, builds parts for jet engines and landing gear for aircraft.

This is a developing story and will be updated.