The Indian Coast Guard deployed four vessels to rescue crew members from the burning Singapore-flagged container ship Wan Hai 503, which was on fire approximately 144 kilometers (90 miles) off the coast of Kerala in southern India.

The crew reported an explosion followed by a fire onboard on Monday morning. The cause of the explosion remains unclear.

Video footage captured from a Coast Guard aircraft showed large plumes of black smoke billowing from the vessel.

Crew members jump overboard to escape flames

The fire reportedly spread to multiple containers, prompting the crew to abandon ship and take to life rafts.

"According to preliminary information ... there were 22 workers on board the ship ... 18 jumped into the sea and are in rescue boats. Efforts are underway to rescue them," said Shekhar Kuriakose, secretary of the state's disaster management authority, according to Reuters.

One of the rescued sailors is reported to have sustained serious injuries.

Four crew members, a Taiwanese national, two Indonesians, and one from Myanmar are still unaccounted for, with a search operation currently underway.

Edited by: Kieran Burke