An examination of a dead whale that was spotted in the East China Sea near Shanghai has found that the animal's left pectoral fin had been severed, possibly intentionally.

Tang Wenqiao, a professor at Shanghai Ocean University, inspected the carcass on Tuesday and estimated that the fin whale had been dead for at least 10 days, according to local media reports.

The whale measured 22 meters long and weighed about 20 metric tons, Tang said, adding that the wounds on its body suggested someone had cut off its pectoral fin.

Fin whales, a protected species in China, usually live in deep waters and are rarely seen offshore, Tang said.

Lu Haibing, a Shanghai-based fisherman, said he first spotted the whale on Sunday, noting that one of its fins was missing. He reported the sighting to police at about 1 pm on Monday and was asked to haul the whale to port.

Police said marine biology experts were asked to investigate the cause of death.

A team from the Shanghai Science and Technology Museum will use the whale as a scientific specimen, a process that will take two and a half years, according to China News Service.

Although the whale is the largest to be found off Shanghai's shore, it is not the first. In 2002, a small whale was found stranded in the Dishui Lake area and had to be helped to return to the sea. A whale carcass was also found near Luchao Port in 1970.

Last week, a sperm whale became stranded and later died in Daya Bay, Guangdong province. An autopsy showed it was pregnant and that its 110-kilogram male fetus had also died.

"It's the first time in the world that an unborn whale calf has been found inside a stranded sperm whale," said Tong Shenhan, head of the Land and Marine Life Research Institute in Xiamen, Fujian province, who took part in the autopsy.

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A dead fin whale found near Shanghai is seen on the banks of the Dazhi River, a waterway in the city, on Wednesday. Experts are due to perform an autopsy on it.Lai Xinlin / For China Daily