An explosion struck a Maltese-flagged oil tanker off the coast of Saudi Arabia today. The crude oil tanker was returning Saudi Port of Shuqaiq to Rotterdam when the vessel was “attacked by an unknown source,” according to the ship’s operators quoted by the Associated Press. 

The explosion did not sink the ship, which is floating off the coast of Saudi Arabia. Officials from the Saudi government have boarded the damaged vessel to investigate the event.

British security firm Ambrey first announced the explosion, attributing it to a mine. Those initial reports are now in doubt as the explosion reportedly occurred one meter above the waterline.

The explosion comes amid continuous fighting in Yemen. A Saudi-backed coalition is fighting the Iranian-backed Houthi rebels who on Monday struck a Saudi oil facility with a cruise missile. 

The bloody conflict between Yemen and Gulf states Saudi-Arabia and the UAE, made possible by Western arms sales, has often witnessed mine explosions. Saudi Arabia has so far cleared 200,000 Houthi mines, a mere fraction of the 1.1 million mines Arab News reported that Houthi forces planted in Yemen.

Combattants in the war in Yemen have not limited the use of mines to land, with Saudi officials reporting the demolition of five Houthi naval mines in the Red Sea on November 24. It remains unclear whether the Saudis missed a Houthi mine that struck the Maltese crude tanker, or whether the vessel was attacked.

Houthi mines remain “a serious threat to maritime security in the Bab al-Mandab strait,” according to the Saudi-led coalition in Yemen.

The MT Agrari is a 243-meter-long crude oil tanker that has its home port in Valletta, Malta. The vessel departed from Rotterdam, the Netherlands at the start of the month, delivering its cargo to Shuqaiq on November 22.  The 11-year-old ship is able to carry up to 107,009 tonnes of cargo but was likely empty when the explosion struck it.

The Associated Press reported that the explosion did not harm the crew but breached the outer hull. “The explosion took place in port limits and punctured the hull of the vessel,” security firm Ambrey told the AP.

Fears of an oil spill in the Red Sea have lingered as the war in Yemen continues. A rusted oil tanker stranded off Yemen’s Hodeidah port could soon spill 1.1 million barrels of crude oil into the Red Sea. The Houthis who control the area have limited any access to the vessels, worsening prospects of fixing the tanker before it spills its cargo.