Fifty-four people were injured and another 18 were missing after an explosion at Qatar's core LNG processing site of Ras Laffan on Sunday, authorities said.

An incident during the start-up of operations at Ras Laffan Industrial City resulted in an explosion and fire at the Barzan local gas supply facility on Sunday evening, QatarEnergy said in a statement. Emergency response teams were deployed to contain the fire, which was now under control, it said.

Qatar's Interior Ministry said in a statement that 54 people had been injured and 18 were missing and being searched for. It attributed the explosion to a "technical accident" and said there was no leak that posed a threat to public safety.

It said the Qatari International Search and Rescue Group, in cooperation with the civil defence teams, was conducting search operations for the 18 missing people.

QatarEnergy did not indicate whether the explosion had caused any damage to the plant, which supplies gas to the domestic market.

A Reuters witness earlier reported that a loud boom was heard in the capital Doha, south of the Ras Laffan facility.