Four workers were taken to hospitals after receiving injuries during an explosion Thursday at the Hazlehurst Wood Pellets plant in Hazlehurst, GA, local news organizations reported.

The blast occurred inside the facility at about 4:30 p.m. and a fire ignited, officials told Fox News affiliate WTGS. Four workers were burned.

Hazlehurst Wood Pellets recently made improvements to the plant’s sprinkler system, which aided firefighters in dousing the flames, Hazlehurst-Jeff Davis County Fire Chief and EMA Director Charles Wasdin said in a report by news broadcaster WJCL.

Reports did not say if dust was a factor in the explosion or not. An investigation into the cause of the incident is underway.

Founded in 2013, Hazlehurst Wood Pellets is a subsidiary of Fram Renewable Fuels LLC. The plant in Hazlehurst was expected to reach its full capacity of 500,000 mt/yr in 2020.