CAIRO (AP) — An explosion at a gas station triggered a massive fire in central Yemen, killing at least 15 people, health officials said Sunday.

The explosion occurred Saturday at the Zaher district in the province of Bayda, the Houthi rebel-run Health Ministry said in a statement. At least 67 others were injured, including 40 in critical condition.

The ministry said rescue teams were searching for those reported missing. It wasn’t immediately clear what caused the explosion.

Footage circulated online showing a massive fire that sent columns of smoke into the sky and left vehicles charred and burning.

Bayda is controlled by Iranian-backed Houthi rebels, who have been at war with Yemen’s internationally recognized government for more than a decade.

Yemen’s civil war began in 2014, when the rebels took control of the capital, Sanaa, and much of the country’s north, forcing the government to flee to the south, then to Saudi Arabia. A Saudi-led coalition entered the war in March 2015, backed at the time by the U.S., in an effort to restore the internationally recognized government.

The war has killed more than 150,000 people including civilians and combatants, and in recent years deteriorated largely into a stalemate and caused one of the world’s worst humanitarian crises.