The US military confirmed on Saturday that the UK-owned vessel Rubymar had sunk after being struck by an anti-ship ballistic missile fired by Yemeni Houthi militants on Feb. 18.
It is the first vessel lost since Houthi terrorists began targeting commercial shipping in November.
"The approximately 21,000 metric tons of ammonium phosphate sulfate fertilizer that the vessel was carrying presents an environmental risk in the Red Sea," US Central Command said on social media platform X.
Yemen's Houthi terrorists have been attacking commercial ships in the Red Sea region since mid-November, saying they are acting in solidarity with Palestinians in Gaza.
On Monday, a Yemeni government team visited the Rubymar, a Belize-flagged, UK-owned cargo ship, and said it was partially submerged and could sink within a couple of days.
The US military previously said the attack had significantly damaged the freighter and caused an 18-mile (29-km) oil slick.
The United States Navy's Fifth Fleet did not immediately respond to a request to confirm the sinking on Saturday.
Mokha port attack on Saturday
In two separate reports on Saturday the United Kingdom Maritime Trade Operations (UKMTO) agency said it had received a report of a ship being attacked 15 nautical miles west of Yemen's port of Mokha.
"The crew took the vessel to anchor and were evacuated by military authorities," the UKMTO said in an advisory note.
Separately, the UKMTO reported a ship sinking.
Neither report named the Rubymar though both incidents occurred in the vicinity of where the Rubymar was last seen.
Houthi attacks have prompted shipping firms to divert vessels on to the longer, more expensive route around southern Africa. They have also stoked fears that the Israel-Hamas war could spread, destabilizing the wider Middle East.
The United States and Britain began striking Houthi targets in Yemen in January in retaliation for the attacks on shipping in the Red Sea, Bab al-Mandab Strait and Gulf of Aden.
Yemen's internationally recognized government is based in the southern port of Aden while the Houthis control much of the north and other large centers.