Almost 50 years after four nuclear bombs fell on the Spanish coast after two US military planes collided, American officials have signed a deal to clean up contaminated land.
None of the bombs detonated in January 1966, but three fell around Palomares and a fourth was found on the sea bed.
Highly toxic plutonium was spread over a 200-hectare (490-acre) area.
On a visit to Madrid, Secretary of State John Kerry agreed to finalise a deal on disposing of contaminated soil.
Under the agreement in principle, signed by Mr Kerry and Spanish Foreign Minister Jose Manuel Garcia-Margallo, the US will remove the soil at Palomares to a site in the US.
Spanish media said the soil would be transported to a site in Nevada. The deal comes a few months before the 50th anniversary of the crash, one of the most serious nuclear incidents of the Cold War.
An earlier consignment of contaminated soil was shipped to a site in South Carolina shortly after the accident and buried in deep trenches.
But further analysis of soil in the area has been carried out in recent years, and the health of residents in the Palomares area is still being monitored.
Spain's Cold War nuclear accident
- On 17 January 1966, a US B-52 bomber carrying four 1.5 megaton bombs collided with a refuelling tanker some 31,000 feet above Palomares on Spain's Mediterranean coast
- The tanker crew and three people on board the bomber were killed
- One bomb equipped with a parachute landed intact
- Two bombs hit the ground at high speed, scattering plutonium
- A fourth bomb landed five miles off shore and was later recovered by USS Petrel
"I looked up and saw this huge ball of fire, falling through the sky" - Spain waits for US to finish nuclear clean-up