( CNN ) -- Almost one week after vanishing en route from Singapore to Vietnam , a Vietnamese oil tanker has been released by pirates who had taken control of the vessel . Nguyen Nhat , director of Vietnam 's Maritime Department , told CNN that the eight pirates who seized the ship absconded with part of the cargo -- 2,000 metric tons of a total 7,200 metric tons of oil . The ship , called Sunrise 689 , had returned to Vietnam with its 18 crew , arriving in port at 5 p.m. local time ( 6 a.m . ET ) . The nationality of the pirates was unknown , he said . The ship 's owners lost contact with the vessel just 40 minutes after it departed Singapore on October 2 , according to the Vietnamese News Service ( VNS ) , citing the ship 's owner , the Hai Phong Seafood Shipbuilding Joint Stock Company . It had been due to arrive in Vietnam on October 5 . VNS reported that Vietnam 's Foreign Ministry had sent `` diplomatic notes '' to the embassies of Singapore , Malaysia , Brunei and Indonesia in Hanoi , asking for assistance in finding the missing ship , which had disappeared from radar . Piracy rising in Asia . Southeast Asia has become a prime target for pirates who have staged a number `` serious attacks '' on tankers in the region , according to the International Maritime Bureau ( IMB ) . According to a report released in July , there had been at least six known hijackings since April , when small coastal tankers were targeted for their cargo of diesel or gas oil . `` The recent increase in the number of successful hijackings is a cause for concern , '' IMB director Pottengal Mukundanm said at the time . Until this year , most attacks had been petty thefts perpetrated on boats anchored at harbor , the IMB said . Sunrise 689 dropped off radar in the middle of a busy shipping zone in the Singapore Strait . According to warnings issued by the IMB , vessels in the Singapore Strait are advised to `` remain vigilant and to continue maintaining adequate anti-piracy / robbery watch and measures . Pirates / robbers attack ships while underway or while at anchor especially during the night . '' CNN 's Elizabeth Joseph contributed to this story .
NEW : Ship , after pirates released it , took off with some cargo . Ship went missing on July 2 within an hour of departing port . 18 crew were on board the ship which was bound for Vietnam .