A ship carrying crude oil that caught fire after being attacked in the Red Sea could lead to a severe ecological disaster, the European Union’s naval force in the region said Saturday.

The Sounion tanker was hit earlier this week by a series of missiles while sailing through the waterway and suffered a fresh attack on August 23, EUNAVFOR Aspides — an EU military operation in response to Houthi engagements with international shipping in the Red Sea — said in a post on X. The vessel now poses “a significant environmental threat” due to the large volume of oil on board, it said. The U.K. Navy reported August 23 that three fires had been seen on board.

On August 22, EUNAVFOR Aspides conducted a Safety Of Life At Sea (SOLAS) Operation as an immediate response to the Sounion’s master’s request for urgent assistance, after it came under attack on August 21, in the southern Red Sea.

“The Houthis’ continued attacks threaten to spill a million barrels of oil into the Red Sea, an amount four times the size of the Exxon Valdez disaster,” the U.S. State Department said in a separate statement.

Yemen’s Houthi rebels have attacked vessels in protest against Israel’s war with Hamas. Although other ships have been sunk, the Sounion risks being the most severe incident given its cargo.

After the first attack on the tanker earlier in the week its crew was evacuated with assistance from a French naval ship. At that time the vessel was anchored in international waters, the EU Navy said August 24, however following the fires on board it was reported to be drifting.