A total of 13 Chinese sailors, who were on two ships hijacked by drug traffickers last week, were confirmed dead after investigators found another body on Mekong River in north Thailand's Chiang Rai Province, local authorities said on Monday.

Searchers found the body in nearby Chiang Khong District early on Monday, said Seramsak Seesan, chief of Chiang Rai's Chiang Saen District, where the other bodies were found.

Investigators suspect that a drug ring of Tai Yai ethnic group led by No Kham was responsible for cargo ship hijacking and killing of crew members, Seesan told Xinhua in a telephone interview.

Autopsies are being conducted in Chiang Saen Hospital.

Relatives of the sailors will arrive later to cooperate in investigation and claim the bodies, he said.

This was the first time a commercial ship was hijacked by drug traffickers, Seesan added.

A committee of police, military and local authorities?are?investigating the incident, he said.?

China's consulate general in Chiang Mai is handling?the incident, a consulate general official said.

The two hijacked cargo ships, the Hua Ping and Yu Xing 8, with 13 crem members, were attacked in the golden triangle area of the Mekong River on October 5,?according to?a statement of China's Foreign Ministry.?

A Bangkok Post report later Sunday said that three bodies of Chinese men, with their hands tied and handcuffed behind their backs, were found floating on the Mekong River in Chiang Rai's Chiang Saen district Friday and another nine bodies were found the day after.??

The Chinese Foreign Ministry in the statement said it has asked the Chinese embassy in Thailand and consulate general in Chiang Mai to investigate the incident immediately and spare no efforts to search for the missing.

Chinese diplomats in Chiang Mai have arrived at the site to start the investigatigation. The Chinese embassy in Thailand and the consulate?general in Chiang Mai?is in close contact with the Thai side to get further information, the statement said.

It has also asked "relevant countries" to take effective measures to improve the protection of Chinese ships and sailors?on the Mekong River, the statement said.

The Chinese Foreign Ministry also said leaders of the Communist Party of China Central Committee and the State Council are paying close attention to the matter.

The ministry has urged the "relevant countries" to immediately look into the incident,?find out?the truth, bring the criminals to justice as soon as possible, and?to ensure safe shipping?along the Mekong River.?