In the midst of the war in Yemen, there is an ecological time bomb ticking just off the coast: a derelict oil tanker that could cause a disastrous oil spill unless immediate action is taken to avert the catastrophe.

Originally used as an offshore storage vessel, the FSO Safer was largely abandoned in 2015 when the Yemeni civil war forced its maintenance and repair operations to come to a halt. After years of decay, aid agencies and environmental groups warn that the rusting tanker—which holds an estimated 1.14 million barrels of oil—is now teetering on the verge of collapse.

If the tanker breaks apart, it could cause one of the largest ocean oil spills in history—bigger than the Amoco Cadiz in France in 1978, the Exxon Valdez in Alaska in 1989, or the Prestige in Spain in 2002—and cost tens of billions of dollars to clean up.