The spokesman, who identified himself only by his surname, Zhao, said the fire ceased around noon. Earlier footage showed huge clouds of thick smoke rising from the oil slick.
Just three bodies from the tanker Sanchi's crew of 32, composed of 30 Iranians and two Bangladeshis, have been recovered.
The cause of the January 6 collision between the Sanchi and the Chinese freighter CF Crystal, which happened 257 kms east of Shanghai, remains unclear. All 21 crewmembers aboard the freighter were reported safe.
The ship was carrying a type of hydrocarbon liquid known as natural gas condensate and left a 10-sq-km area contaminated with oil, according to Chinese authorities.
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Condensate is highly toxic but readily evaporates or burns off in a fire. If trapped underwater, however, it could seriously harm the marine environment, while the ship's fuel source also poses a major threat.
The ship's voice data recorder, which functions like a "black box" on aircraft, was reportedly recovered on Saturday, possibly helping shed light on how the collision and resulting fire occurred.
Chinese state broadcaster CCTV said rescue operations had been converted at noon to a search-and-recovery effort. Two ships were on the scene spraying foam detergents to dissolve oil remaining on the surface.
The disaster has transfixed an Iran still reeling from days of protests and unrest that swept the country at the start of the year.
Families of the sailors wept and screamed at the headquarters of the National Iranian Tanker Company in Tehran, the company that owns the Sanchi. Some needed to be taken by ambulance to nearby hospitals as they were so overwhelmed by the news.
Iranian President Hassan Rouhani and Supreme Leader Ayatollah Ali Khamenei both expressed their condolences, with Rouhani calling on relevant government agencies to investigate the tragedy and take any necessary legal measures.
The government also announced today as a nationwide day of public mourning over the disaster.
Chinese officials blamed poor weather for complicating their rescue efforts. Thirteen ships, including one from South Korea and two from Japan, had joined in the rescue and cleanup effort.
It's the second collision for a ship from the National Iranian Tanker Comapny in less than a year and a half. In August 2016, one of its tankers collided with a Swiss container ship in the Singapore Strait, damaging both ships but causing no injuries or oil spill.