Houston, Apr 20 (IANS): Three contractors were injured with varying degree burns after a chemical plant set blazed near Houston, US state of Texas, authorities said.

Kinder Morgan officials said on Friday that the fire occurred at its petroleum facility in Galena Park during planned maintenance work near one of its rail racks, and was immediately extinguished, Xinhua news agency report.

The victims were third-party contractors, and Harris County Judge Lina Hidalgo said they sustained varying first through third-degree burns, according to an ABC13 News report.

The impacted portion of the rail rack has been isolated and shut down, Kinder Morgan said.

The exact cause of the fire remains unclear.

Officials said that flash fires often happen when a flammable chemical mixes with air and encounters a heat source. The heat source can be as basic as static electricity.

Kinder Morgan stands as one of the largest energy infrastructure companies in the US.