AUGUSTA, Ga. -- Another burn patient has died of injuries suffered in an explosion and fire at a sugar refinery, bringing the death toll to 13.

A little more than a month after the Feb. 7 blast at the Imperial Sugar plant in Port Wentworth, six other patients remained Friday in critical condition at the Joseph M. Still Burn Center at Doctors Hospital in Augusta. Officials said four are in serious condition.

The patient's name was not released.

The explosion destroyed the packaging area where workers poured sugar into bags sold under the Dixie Crystals brand. The refinery itself, used to turn raw sugar into consumer-ready crystals, sustained less damage but remains shut down.

The fire was so intense, local firefighters had to call on a Texas company to snuff out the blaze before it spread. The company hauled in specialized equipment that pumped out 6,000 gallons of water and foam a minute.

Officials have not yet determined what ignited the explosion. Investigators have said the explosion was fueled by airborne sugar dust.

Earlier this week, Chemical Safety Board executive William Wright said "snow-like" accumulations of industrial dust were reported at the plant and that simple housekeeping probably would have prevented the blast.