The oil, estimated to weigh one ton in total, was discovered Friday in Ky Loi Commune of Ky Anh Town.
The oil was swept ashore by the waves, ending up on a stretch of beach between Hai Phong 1 and Hai Phong 2 villages.
Nguyen The Anh, deputy chairman of Ky Anh Town, said there have been no reports of sunken fuel vessels in local sea regions over the past few days.
On Saturday, authorities deployed dozens of people to the site to clean up the beach, with the process lasting around four hours. Experts have also been dispatched to figure out where the oil came from.
Oil, if not properly cleaned up, can impact seawater quality and cause pollution in surrounding areas. Oil had previously been found at certain beaches in the central provinces of Binh Thuan, Khanh Hoa, Quang Tri and Phu Yen.
In 2019, about 3 km of Ky Anh Town beach was stained with oil spilled by the sunken cargo vessel Nordana Sophie HSCP2 near Son Duong Port. The vessel had been carrying 178 tons of oil.