A spokesman for the Kuwait Petroleum Company (KPC) claimed significant progress in removing the oil from last week’s oil spill off Kuwait’s southern coast, Kuwait Times reports.

“The major portion of the main oil spill has been removed,” KPC spokesman Sheikh Talal El Khaled El Sabah, said in a statement reported by the Kuwait Times. He added that clean-up work was still continuing in coastal areas and other areas of the spill.

The size of the spill is currently unknown, but experts interviewed by Kuwaiti media estimated it could have been as large as 35,000 barrels, according to The National.

Kuwaiti officials are investigating the cause of the spill. The head of the Environment Public Authority, Sheikh Abdullah al-Sabah, told the Associated Press that “[t]here will be severe consequences to those responsible for this incident, and we will prosecute them,” ABC News reports.

Initial clean-up efforts focused on protecting Kuwait’s local water-desalination and power plants, Reuters indicates.

The leak occurred in the Ras El Zour region in southern Kuwait.