A massive fire has broken out at one of Indonesia's largest oil refineries, creating a towing inferno and dark plumes of smoke and toxic fumes. Some experts say lightning could have sparked the fire and explosion.

At least 20 people have been injured, five of whom are in intensive care after suffering severe burns, and around 950 local residents have also been evacuated from their homes, according to the BBC. Three people are still missing and another is reported to have died from a heart attack during the traumatic event, according to the Guardian.

The fire began at 12:45 a.m. local time on Monday, March 29 (1:45 p.m. ET Sunday March 28) at the Balongan refinery on the island of West Java; the refinery is capable of processing 125,000 barrels of crude oil per day, most of which is sent to the capital Jakarta 140 miles (225 kilometers) to the west, according to Reuters.

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Firefighters managed to contain the blaze to just four of the 72 gasoline storage units at the site and stop the inferno from spreading across the entire facility, according to Reuters. But the fire still continues to burn and produce dense clouds of black smoke.

Aerial photo shows thick smoke rises due to fire at Pertamina's Balongan oil refinery. (Image credit: Muhammad A.F/Anadolu Agency via Getty Images)"The cause of the fire is not known with certainty, but at the time of the incident, it was raining heavily accompanied by lightning," Pertamina — the state-owned oil company that runs the refinery — said in a statement.

However, the local police suspect that oil may have leaked out of one of the tanks and was then ignited by the lightning.

"Initial information we received is that there was a leak at the plant," Ahmad Dofiri, chief of police for West Java, told Reuters. "While the leak was being handled, the lightning struck."

Reports from evacuated residents also support the theory that leaked oil may have been ignited by lightning.

"We smelled a strong fuel scent first, so strong that my nose hurt," a local woman known only as Susi told local news channel Metro TV, according to Reuters. "We heard lightning strikes, suddenly the sky was orange."

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As soon as the flames have been completely extinguished, local authorities will begin a full investigation to figure out how the fire started, according to Pertamina. The company also said that the refinery will be up and running soon and assured the public that there will be no shortage of oil in the country.

"The main equipment at the refinery is not affected," Nicke Widyawati, CEO and director of Pertamina, told Reuters. "We hope the plant can be operational again soon after we put out the fire so there are no disruptions to supply."

Originally published on Live Science.