A U.S. Navy ship mistakenly shot down an American fighter jet over the Red Sea early Sunday, the U.S. military said, highlighting the potential risks for international forces as they try to stop attacks on cargo ships by the Houthi militia in Yemen.

The U.S. military’s Central Command described the incident as an apparent case of friendly fire and said that the two pilots had been safely recovered after they ejected from their F/A-18 aircraft. One had minor injuries, Central Command said in a statement, adding that an investigation was underway. The incident occurred during a refueling operation, a Department of Defense official said.

The jet had flown off the aircraft carrier Harry S. Truman when it was mistakenly fired upon by the guided-missile cruiser Gettysburg, the command said.

Both ships are in the Harry S. Truman carrier strike group. The U.S. military said Dec. 15 that the group had been deployed to its area of responsibility, which includes Yemen and the surrounding waters. It did not specify where the group was located.

The apparent incident of friendly fire came after Central Command said Saturday that it had conducted airstrikes against a Houthi missile storage facility and a command facility in Sanaa, the capital of Yemen. It said it had also shot down multiple Houthi unmanned aerial vehicles and anti-ship cruise missiles over the Red Sea.

The Houthi militia, which is backed by Iran, controls much of northwestern Yemen and has been striking ships with missiles and drones for over a year in what it has described as a campaign in solidarity with Palestinians under Israeli bombardment in the Gaza Strip. The attacks on shipping have disrupted one of the busiest maritime routes in the world, forcing many vessels to avoid the area.

The U.S. military, sometimes joined by British forces, has conducted multiple strikes this year on Houthi targets in Yemen in an effort to secure international waterways. Those have so far failed to halt the militia’s ability to strike targets far beyond the territory that they control.