At least six others injured and authorities unable to confirm if there was an oil spill because of poor visibility after nightfall.
One person was killed and six injured after an oil tanker exploded east of Hong Kong on Saturday.
According to the Hong Kong Government Flying Services, it was notified of an explosion at 4:05pm (08:05 GMT) on an oil tanker in waters 300km (186 miles) to the east of Hong Kong.
The cause of the blast was unclear as of Saturday night, a government spokesperson said.
A fire on the oil tanker was put out by the time rescuers arrived, AFP news agency quoted the spokesperson as saying, adding the ship had lost its mobility. Authorities were unable to confirm if there were oil spills because of poor visibility after nightfall.
Authorities dispatched a fixed-wing aircraft and two helicopters to rescue seven crew members reported to be injured.
One man had died by the time rescuers arrived at the Panama-registered ship, the 5,547-tonne Chuang Yi.
Three Indonesian men in their 30s were seriously injured, including one with second-degree burns covering 30 percent of his body and others with burns on their faces.
Two other Indonesian men and a man from Myanmar, all aged between 30 and 40, had less serious injuries such as lacerations and burns.
According to ship tracking apps, the oil and chemical tanker was on its way to Taiwan. The 120-metre (390-foot) long vessel is 22 years old.