CORRIGAN, Texas -

Four people remain hospitalized, three in critical condition, after an explosion and fire at a Polk County plywood mill.

According to Eric Abercrombie, a spokesperson for Atlanta-based Georgia Pacific, seven people were injured when the fire broke out around 6 p.m. Saturday at the Corrigan plant. Four were flown to Memorial Hermann Hospital in Houston and three others were taken to a Lufkin hospital.

A spokesperson for Memorial Hermann said three of the patients were listed in critical condition Sunday. The fourth was listed in fair condition. The workers taken to Lufkin were treated and released Saturday night, according to Abercrombie.

OHSA investigators were at the plant Sunday to begin their investigation. Abercrombie said the accident happened in a bagroom, a silo-like building that collects dust from the sanding process.

“The doors on the circumference of the building were designed to release the buildup of energy. It did that, they vented out. The dust inside is made of wood, it's combustible. So, there was a buildup. We're not sure what caused that, we're in the process of investigating that,” said Abercrombie.

While the investigation is underway, operations at the plant have shut down. The plant employs about 400 people.

“It's a bad thing for the community that people got hurt, especially people you know. You hate to see anybody get hurt,” said Corrigan resident Larry Torrez.

Abercrombie said the company's thoughts and prayers are now with the injured workers and their families. Georgia Pacific is handling accommodations for the families so they can be with their loved ones in Houston.