At least six tonnes of clotted oil, spread over seven kilometres of central Quang Tri province's beaches, were collected on April 7, the provincial Department of Natural Resources and Environment said.

On April 3, oil curdles appeared along the seashore of the province from Vinh Linh to Gio Linh districts. The volume of oil curdles that washed ashore was estimated to be about eight tonnes.

The cause for the phenomenon was yet to be identified, the department said.

It asked local authorities to mobilise local residents and young people to collect oil curdles along 3.5km of the beaches in Vinh Thach and Vinh Kim communes in Vinh Linh district.

In Gio Linh district, two tonnes of oil curdles were collected and 80 percent of the oil spill was cleaned up.

Nguyen Truong Khoa, deputy director of the department, said the department had checked the area where the clotted oil had spread on the beach and offered supporting equipment to help make the task easy.

The collected oil will be transported to the central Oil Spill Response Centre for treatment.

The appearance of the curdled oil along the 75km long coast of Quang Tri province occurred between in 2007 and 2009, with the estimated volume of oil pegged at more than 20 tonnes.-VNA