The “expatriates,” mostly well-paid Western workers, were eligible for $300,000 in accidental death and disability insurance. The “third country nationals” from Nepal and India, and “local nationals” from Afghanistan, could claim only $30,000, according to the lawsuit and a copy of a document from Sabre outlining the categories.

After the attack, the men said, only $30,000 was deposited into their bank accounts. The workers said Sabre representatives told them they were not entitled to more under the latest contract. Sabre later stopped answering calls and emails, the men said.

“This was the first time any of our clients had ever seen that contract,” Mr. Fiorante said.

Matthew Handley, an American workers’ rights lawyer assisting with the case, said it was common for security companies to exploit contractors from poor countries where labor laws are weak. In general, he said, when workers get injured or killed on the job, companies “throw them on the plane back to their home country and hope that they’ll never hear from them or their families again.”

There had been prior signs of trouble for the guards in Kabul. According to the lawsuit, when Sabre did not distribute updated employment contracts a few years ago, contractors reached out to Deborah Lyons, then the Canadian ambassador there.