Explosions rocked Royal Dutch Shell's largest oil refinery on Thursday, forcing the closure of several refining units and the evacuation of most staff as a fire at the Singapore plant continued for a second day.
Witnesses told The Straits Times newspaper that they heard three large blasts around midday and saw a "fire ball shooting into the sky."
A blaze that broke out Wednesday at the 500,000 barrel-a-day refinery on Bukom, an island 3 miles (five kilometers) offshore, had appeared to be brought largely under control.
But there was a new surge on Thursday.
Refinery units near the blaze had been shut down as a precaution, Shell said, and only essential staff would remain on Bukom.
"The source of the fire are remnant light fuel components within the specific area where the fire originated," Shell said in a statement on its website.
There have been no reports of injuries.
Singapore is one of the world's top 3 centers for the refining and export of oil and is Asia's main oil trading hub.