A powerful blast at a Zodiac Aerospace factory in Washington state made some portions of the building unsafe to enter, raising concerns that the assembly of Boeing and Airbus aircraft could be affected.

Boeing and Airbus said on Wednesday they were assessing the potential impact of the factory closure on their operations, since it supplies materials used in aircraft interiors.

The explosion that rocked Zodiac’s Newport, Washington, plant was felt miles away, injured at least seven people and prompted the evacuation of surrounding homes and businesses for about four hours due to strong chemical odors, officials said.

“There’s no recommendation to enter the building,” Grant Sirevog, undersheriff for Pend Oreille County, told Reuters. “The structural integrity is greatly compromised.”

The blast at around 9 pm (0400 GMT) Tuesday night caused one floor of the low-rise factory to collapse, fractured concrete supports, blew out windows and lifted the roof, Sirevog said.

Seven people were taken to hospitals from the incident, including two who were transferred to a trauma facility in Spokane, Newport Hospital Records Manager Julie Lohman said. The rest were treated and discharged.

One of the victims sent to Spokane underwent surgery and was in critical condition on Wednesday, Sirevog said.

The building, about 100 yards (91 meters) long by 30 yards (27 meters) wide, has been turned over to Zodiac officials, he said.

The plant produces resin-impregnated honeycomb core and composite panels used by numerous Zodiac facilities to make aircraft lavatories, galleys and other structures, according to two people familiar with its operations.

Zodiac, based in Plaisir, France, said in a statement that it was investigating the cause. “Our first thoughts go to our colleagues who have been injured,” the company said.

Zodiac is a major global supplier of aircraft seats, interiors and other components, and has come under scrutiny recently for production problems at its cabin interiors and seats factories in the U.S.

The problems caused delays in deliveries of Boeing and Airbus jetliners, and prompted Zodiac to warn recently that its profits would fall short of earlier targets.

The explosion stemmed from flammable chemical vapors that ignited, authorities said. Sirevog said a “treater” machine used to impregnate materials with resin was operating but another machine to burn off the vapor appeared to be switched off or not working, allowing vapor to build up.

There were about 15 people in the plant when the blast occurred, he said, adding the injuries could have been greater.

“Everything close to where the blast occurred was fractured,” said Brian Schaeffer, assistant chief for the nearby city of Spokane fire department. He described the blast as far greater than explosions caused by natural gas leaks in homes.

“I’ve never seen that amount of force exerted on a structure in my career” of more than two decades, he said.