WASHINGTON — An appeals court will force Veterans Affairs officials to identify how many troops may have been exposed to radioactive debris from a 1966 plane crash, a move that supporters hope will be the precursor to a class-action lawsuit against the department for overdue benefits.

On Tuesday, the U.S. Court of Appeals for Veterans Claims made the unusual ruling demanding the records' release six weeks after VA lawyers argued the information is nearly impossible to obtain, given aging and missing military records from the accident.

But the court, by a 6-3 ruling, gave the department 30 days to determine the number of military personnel assigned to the accident clean-up, the number of veterans who have applied for benefits connected to the event, and the number who have been denied compensation. That information will be used to decide how a lawsuit on the benefits denial may proceed.

Veterans involved in the accident have been unsuccessfully petitioning VA on their case since the mid-1970s, after a host of strange cancers and other illnesses began appearing among individuals involved.

In January 1966, seven airmen were killed and four more injured when a B-52 crashed into a KC-135 during a refueling mission off the coast of Spain. The B-52 was carrying four nuclear weapons at the time of the accident. The non-nuclear explosives in two of the weapons detonated upon impact with the ground near the town of Palomares, spreading radioactive plutonium over hundreds of acres.

U.S. officials quickly ordered military personnel into the area to collect contaminated debris, crops and soil in an effort to repair the damage. But veterans involved in that cleanup say they were given no protective clothing or respiratory devices, and told very little about the potential long-term health effects from exposure to the nuclear material.

Earlier this year, the appeals court ruled in a separate case that veterans can file suit against the Department of Veterans Affairs as a class rather than individuals, in limited circumstances.

Since then, legal experts have been monitoring a host of lawsuits before the court to see which could be the first class recognized, a move which will set important precedents for future legal cases.

The three judges who argued against the records request in the Palomares lawsuit said the move would effectively force VA to justify the need for a class-action lawsuit against itself, and that the majority ignored concerns that Defense Department records for the incident may not exist.

But the majority opinion noted that no final decision on whether to recognize a class of Palomares has been made, and data on the denied benefits is the sole property of VA, inaccessible in any way for outsiders.

Plaintiffs in the lawsuit have contended that more than 1,600 veterans should be eligible for disability benefits related to the toxic exposure, but VA thus far has denied their requests because not enough scientific evidence exists to classify all of the health problems as service-related illnesses.