HARTFORD, Conn. — Veterans groups sued the Defense Department on Tuesday in an effort to obtain disability benefits for airmen who say they were exposed to radiation while responding to a 1966 accident involving U.S. hydrogen bombs in Spain.

The lawsuit filed in federal court in Connecticut says many of the 1,600 airmen who responded to the accident have been unable to obtain disability benefits for radiation-related illnesses because the Defense Department has refused for five decades to release medical testing results and other information.

A Defense Department spokesman said he could not comment on pending litigation.

The lawsuit was filed by Yale Law School students representing Vietnam Veterans of America, the group’s Connecticut chapter and Anthony Maloni, a 72-year-old veteran airman from Agawam, Massachusetts.

The veterans groups are seeking a court order compelling the Defense Department to release records under the federal Freedom of Information Act relating to the accident, including results of urine sampling from the airmen and environmental testing data. The department has failed to respond to requests for the records, according to the lawsuit.

On Jan. 17, 1966, a U.S. B-52 bomber and a refueling plane crashed into each other during a routine refueling operation near the southern Spanish village of Palomares, killing seven of 11 crew members. There were no fatalities on the ground.

The midair collision resulted in the release of four U.S. hydrogen bombs. None of the bombs exploded, but the plutonium-filled detonators on two went off, scattering 7 pounds (3 kilograms) of highly radioactive plutonium 239 across the landscape.

The 1,600 airmen were sent to the crash site area to recover the weapons and were exposed to dangerous levels of radiation daily for weeks or months at a time, according to the lawsuit. Many of the airmen later developed various forms of cancer, blood disorders, heart and lung dysfunction and other sicknesses, but were denied disability benefits by the Department of Veterans Affairs, the lawsuit says.

Maloni was 21 when he went to Palomares. Afterward, he developed psoriasis, eczema, alopecia, bronchitis, high blood pressure and ischemic heart disease, and began experiencing excruciating headaches and migraines, the lawsuit says.

“Palomares veterans have waited decades for even basic information about the medical risks that prolonged exposure to radioactive plutonium dust carries,” said Patti Dumin, president of the Connecticut State Council of the Vietnam Veterans of America. “They cannot wait any longer. The Pentagon owes them answers.”

The lawsuit also says the Air Force failed to protect the airmen from the radiation and warn them about the danger. Although the Defense Department collected urine samples from the airmen, it never shared the results with most of them, the suit says.

The Defense Department also has maintained that the airmen’s radiation exposure was too low to have triggered diseases, despite many urine samples showing dangerously high exposure levels, the lawsuit says.