The fire was reported around 10:30 a.m. at Kuraray America, Inc. plant located at 11500 Bay Area Blvd.
At the time of the incident, approximately 250 employees and contract personnel were onsite, according to plant officials.
Officials say all employees have been accounted for.
According to authorities on the scene, 20 people were taken to hospitals by ground with non-life threatening injuries ranging from knee injuries to burns, and two were taken by Life Flight with slightly more serious injuries.
A Pasadena fire official told Eyewitness News that the flash fire was caused by a broken valve.
The company says they are fully cooperating with all local authorities and emergency response teams, and will provide additional information as it is confirmed.
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