The cause of an explosion in January at Ivex Protective Packaging that injured three people has been determined.

Firefighters responded the blast late Jan. 25. Two sides of the building were blown out, and three people suffered minor burns and were taken to Wilson Memorial Hospital.

Fire officials said today that the investigation has been completed, and the explosion was a result of the release of non-odorized, flammable isobutane gas in the building. The released gas was then ignited from an unidentified source.

The gas release originated in an area of the building where isobutane is injected into molten plastic, according to a release.

The cause of the gas release and explosion is accidental.