SAN ANTONIO, TEXAS- A San Antonio refinery operator says a contractor installing some tubing set off a fire that forced 60 workers to evacuate.

NuStar Energy spokeswoman Mary Rose Brown said Wednesday the refinery didn't appear significantly damaged. She said the fire started when a dislodged valve released a small amount of kerosene, which then vaporized and ignited. No injuries were reported.

It was the second fire at the refinery in two years. A series of explosions at the plant in May 2010 left one man critically burned and caused surrounding homes to evacuate. NuStar was not the refinery owner at the time. Brown said the company does not yet know when the plant will start back up.