Thai navy vessels were scrambled early Sunday to contain hundreds of barrels of crude oil that spilled into the sea off the eastern province of Rayong.

PTT Global Chemical Plc (PTTGC) said roughly 50,000 liters of crude oil leaked into the sea when a tanker was loading crude to the offshore pipeline Saturday morning, reports Bangkok Post.

Marine Department director-general Sorasak Saensombat said more than 10 ships were sent to clean up the oil slick, about 800m wide and 2.5km long, which occurred 20 kilometers off shores southeast of the Map Ta Phut industrial estate.

The hastily assembled flotilla, which included five company boats and five other vessels from the Royal Thai Navy, sprayed oil spill dispersants to stop the slick from reaching a major tourist beach in Muang district.

Planes from Singapore’s Oil Spill Response Co. were also deployed to speed up the operation after 30-40% of the slick had been removed.

By Monday, the oil slick was contained to about 500m and 1km long, Rear Admiral Thiwa Daramuang, chief-of-staff of the First Naval Area Command, said.

But the oil spill had already reached Prao Bay in Koh Samet Island, another popular tourist destination in the Gulf of Thailand, where the slick has blackened the water and the sandy beach.