The attorney for a State Department contractor jailed in Cuba said his client may be suffering from cancer.

Alan Gross is serving a 15 year sentence in a Havana jail for bringing in banned communications equipment to the island.

In recent weeks Gross' family and attorney have said his health is failing and that he has suffered significant weight loss since his arrest three years ago. On Tuesday night, Gross attorney Jared Genser issued a statement saying a mass of tissue on Gross' right shoulder could be cancer.

"Cuban government doctors are either guilty of gross professional negligence or they are intentionally hiding what could be a lethal condition," Genser said in the statement.

According to the statement, Gross Cuban medical records were examined in the United States by a doctor hired by his legal team.

The Cuban government last month said Gross' health was "normal." He is serving his sentence in a military hospital.

Cuban officials also said last month that they wished to negotiate Gross' case and that of five Cuban intelligence operatives held in the United States.

U.S. government officials have rebuffed any suggestion of a prisoner swap and instead called for Gross' immediate release.