Bright crimson moonlight dappling Mekong River mirrored the sadness of the relatives who were saying goodbye to the Chinese sailors killed after their cargo ships were attacked by suspected drug traffickers on the Mekong River near Golden Triangle on Oct. 5. At the memorial service, the 29 relatives of the 13 Chinese sailors -- 12 killed and another still missing -- gathered at the riverside in northern Thailand\'s Chiang Saen district, burning joss paper and flying Kong Ming lamps and paper balloons to bid farewell to their beloved. In Chinese folklore, when one dies far away from home, part of his soul remains on the site, holding on for the last reunion with his beloved ones. He Xilun, like others, came with an empty stomach, said: \"My brother has not eaten anything for so many days. How can I eat, knowing that he\'s waiting for me right there?\" His elder brother He Xihang was among the 12 sailors slain during an attack by an unknown group of armed men on two commercial ships on Mekong River. One sailor is still missing. The search for the missing is still under way. The family members arrived here from southwest China\'s Yunnan province at around 6 p.m. Thursday after more than 10 hours of traveling by water and bus. They declined a dinner arranged by Chinese officials and went for the memorial service without delay. The two cargo ships, Hua Ping and Yuxing 8, floated quietly at a small port. All the relatives burst into tears when they saw the ships, with some fainting. \"My dearest big brother (caring lover), how can you leave me like this? I\'m lonely without you,\" wife of Cai Fanghua, a slain sailor on Hua Ping, sobbed out. The family members also unrolled a banner at the site reading \"find out the truth, punish the killers.\" A working group dispatched by southwest China\'s Yunnan province has arrived in Chiang Saen County to assist the Chinese embassy in Thailand and the consulate general in Chiang Mai in dealing with the incident, Chinese Foreign Ministry Spokesman Liu Weimin said on Tuesday. Liu said Thailand has promised it will fully cooperate with China and do its utmost to ensure safety on the Mekong River to prevent similar incidents from happening in the future. On Thursday, Chinese Vice Foreign Minister Song Tao summoned diplomatic envoys from Thailand, Laos and Myanmar and urged the three countries to intensify their investigation of the deadly attack. Song said all three countries should \"unearth the truth\" regarding the incident as quickly as possible and provide China with timely reports during the investigation. Song also said China has urged the countries to take effective measures to strengthen the protection of Chinese ships and sailors on the Mekong River and its surrounding waters. Envoys from the three nations expressed condolence for the killed Chinese sailors. All three countries will coordinate with China to carry out an active investigation and properly handle the aftermath of the incident, the envoys said. The 164 Chinese sailors and 28 cargo ships stranded at the Chiang Saen port set out for home Friday morning under the escort of Chinese patrol vessels.