HANGZHOU -- Rescuers salvaged four more corpses from the Qiantang River in east China's Zhejiang Province early on Saturday, bringing the death toll in the rising tide on the river on Thursday to 12.

The newly found remains were salvaged from the water area one to five km downstream the place where the tidal current first rose and swept away more than 30 people who were either swimming in the river or strolling around on the embankment.

Rescuers received 11 reports of missing people from family members or partners after the accident, the bodies of whom now have all been found, said Xie Liewei, deputy head of Jianggan District, Hangzhou, where the accident occurred.

Local police is still checking the identity of the other body, a male who was not among the reported, Xie said.

"No new reports of missing people have been received," said Xie. But he said searching work is still going on, as many people at the site had come alone or without telling others of their whereabouts.

An office has been set up to register more reports from family members.

All the dead and the missing are believed to be Chinese, according to Xie.

The district is organizing workers to build iron barriers at the entrances to the eight T-shaped levees of the river, including the one where the tragedy occurred.

The barriers, which will be completed within two days, will prevent people from nearing the embankments, Xie said.

Twenty-two people were rescued after the tidal bore swept away dozens of 30 people who were either swimming in the river or walking along a T-shaped levee near the mouth of the Qiantang River on the outskirts of Hangzhou.

The tides on the Qiantang are a peculiar phenomenon and always attract spectators. Scientists say that the trumpet-shaped mouth of the Qiantang River helps form the tidal change, which can be as high as 3.5 meters.

The tragedy occurred on Thursday afternoon when the tide was moving at a normal speed of 15 km per hour, which appeared "mild" from a distance, said Zhou Guangming, a tide expert.

However, its power reached up to four to seven tons per cubic meter when it rushed into the trumpet-shaped levee.

Most of the victims and the missing were from other parts of China as local residents were usually aware of the danger and never risked their lives in the river, said Zhou.

Experts attribute the formation of powerful tidal currents in the river in recent years to the accumulation of silt washed down in the Yangtze River, the change of the water course, the strong wind that always accompanies the tide and floods upstream.

The worst tidal accident occurred on October 3, 1993, when the tidewater swept 86 people from the levee, leaving 19 dead, 40 missing and 27 injured.

The local government has hired a group of local people to patrol the river and warn people of the danger of incoming tides.

Ren Baojin, an elderly man who worked for about ten years as a "tide shouter", said he and his colleagues shouted out when the tide was approaching, but many people, especially those from other regions, often ignored the warning.

The local government has ordered round-the-clock patrols along the river and reinforcement of supervision at dangerous sites. Warning signs will be erected to keep people away. It was also suggested that all the levees along the river should be closed, said public security bureau officials.