Both Ramirez and workers said there had been injuries, but gave no more details.

Emergency workers were at the scene, where smoke and flames could be seen over the facility. Inhabitants of the immediate area were being evacuated, authorities said.

Ivan Freites, a union leader at the state oil company PDVSA, said foam would be used to control the fire.

PDVSA has struggled with repeated refinery problems in recent years, affecting its production figures and ability to fulfil ambitious expansion plans.

Power faults, accidents and planned stoppages for maintenance have hit exports from South America's biggest crude producer and OPEC member.

The Associated Press and Reuters contributed to this report.