Authorities in China are cleaning up one of the worst ever oil spills in Chinese waters.
The collision ripped a hole in the hull of the German-registered ship
Some 524,000 litres (138,000 gallons) of crude oil has leaked in the South China Sea some 15km (nine miles) from the mouth of the Pearl River.
The oil spill occurred when a German-registered container ship, MSC Ilona, collided with the Panamanian-registered Hyundai Advance overnight on Tuesday.
The hull of the German vessel was punctured, spewing out its oil cargo.
The Panamanian ship had initially tried to escape from the scene of the accident but was traced by Chinese maritime authorities hours later.
An official told Reuters news agency it was the worst leak in half a decade.
"It is the worst ocean pollution even in five years," a spokesperson from the Ministry of Communications said.
The 75,500-ton MSC Ilona was on its way to the southern Chinese city of Shenzhen from Shanghai when the accident occurred.
The spill has now spread to an area of up 16km (10 miles) long and 200m (660 feet) wide, according to the Associated Press news agency.
Strong winds and high seas have hampered clean-up efforts which are expected to continue for several days.