A 45-year-old engineer who suffered major burns to his face following a chemical explosion at Agilent Technologies in Santa Rosa remained in critical condition Thursday at a Sacramento burn unit as state and local investigators begin a lengthy investigation into what caused the blast.

Patrick Colbus was working on a molecular beam epitaxy machine Tuesday morning when the explosion occurred. The explosion involved several highly reactive chemicals used by the device to coat integrated circuits. That initially caused concern that the building was contaminated and workers could have been exposed to toxic chemicals.

The investigations will look into whether Agilent followed state and local regulations guiding the use of hazardous materials.

"They could take months to complete these investigations. These are very high stakes," said Toby Rey, an investigator with the Santa Rosa Fire Department.

The fire department monitors the approximately 300 businesses and agencies in the city that use hazardous materials or produces toxic waste, Rey said.

CalOSHA investigators were called to the scene and have begun what could be a six-month process.

They will interview employees, review the company's accident and injury records, scrutinizing their health and safety plans, an agency spokeswoman said.

"We take a look at all of that documentation and then to try to determine what circumstances led up to the accident and if there were any health and safety violations," said Krissann Chasarik with CalOSHA.

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