MADRID (AP) — Spain and the United States have agreed to discuss further cleaning up and removing land contaminated with radioactivity after a mid-air collision in 1966 dumped four U.S. hydrogen bombs near the southern Spanish village of Palomares.

Under a statement of intent signed Monday by Foreign Minister Jose Manuel Garcia-Margallo and U.S. Secretary of State John Kerry, the two countries will negotiate a binding agreement to further restore and clear up the Palomares site and arrange for the disposal of the contaminated soil at an appropriate site in the United States.

The bombs were released on Jan. 17, 1966, when during a routine refueling operation a U.S. B-52 bomber and a refueling plane crashed into each other, killing seven of 11 crew members.