Fears of disrupted global shipping turned to fears of environmental disaster on Saturday, as a cargo ship struck by Yemen’s Houthi rebels sank into the Red Sea. The British vessel Rubymar was carrying 21,000 metric tons of fertilizer when it was hit by a Houthi missile on Feb. 18. The attack caused it to slowly sink until it finally capsized Saturday morning, U.S. Central Command (CentCom) said. “The approximately 21,000 metric tons of ammonium phosphate sulfate fertilizer that the vessel was carrying presents an environmental risk in the Red Sea,” CentCom added. The vessel left an 18-mile long oil slick in its wake and had been abandoned by crew after the attack last month. Julien Jreissati, a top Greenpeace director for the region, warned that ship could destabilize marine ecosystems with “cascading effects through the food web” and called on emergency teams to be allowed to respond immediately. The ship is believed to be the first vessel lost completely because of Houthi attacks.