WASHINGTON (AP) — Two U.S. Navy SEALs are missing after conducting a nighttime boarding mission Thursday off the coast of Somalia, according to three U.S. officials.

The SEALs were on an interdiction mission, climbing up a vessel when one got knocked off by high waves. Under their protocol, when one SEAL is overtaken the next jumps in after them.

Both SEALs are still missing. A search and rescue mission is underway and the waters in the Gulf of Aden, where they were operating, are warm, two of the U.S. officials said.

The U.S. Navy has conducted regular interdiction missions, where they have intercepted weapons on ships that were bound for Houthi-controlled Yemen.