Houston, TX — Crews battled a stubborn fire at a BP plant outside Houston, Texas, Tuesday afternoon.

The refinery in Texas City caught fire, sending a huge, black plume of smoke over the area for hours while firefighters worked to douse the flames.

Officials say they had a tough time putting out the fire because the oil burning has turned into a tar-like substance.

The cause of the fire is under investigation.

No injuries have been reported.