WASHINGTON (Reuters) - The U.S. Department of Homeland Security said on Wednesday it is considering a request by members of Congress to waive federal restrictions on shipping to Puerto Rico, but has not received any formal requests from shippers or other branches of the federal government to waive the law. “We are considering the underlying issues and are evaluating whether a waiver should be issued,” said a senior Homeland Security official, who spoke to reporters on the grounds of anonymity. The Jones Act requires that all goods shipped between U.S. ports be carried by American owned-and-operated ships. Several U.S. lawmakers, including Representative Nydia Velazquez, on Monday asked DHS to waive the Jones Act restrictions for a year to help relief efforts in Puerto Rico where people are suffering from water and food shortages in the wake of Hurricane Maria. But a request from a member of Congress is not the usual pathway by which the department gets waiver requests, the DHS official said. Puerto Rico has long railed against the Jones Act, saying it raises the cost of imported basic commodities, such as food, clothing and fuel. But the official said that the Defense Department and FEMA have not indicated there is a lack of ships to get food and goods to the island. The official did not deny that the law can add costs to goods delivered to the island, an argument made by longtime opponent of the Jones Act, Republican Senator John McCain. But the DHS official said Jones Act exemptions are based solely on the interest of national defense.  “The real challenges happen to be on the island itself,” the official said, adding that there were plenty of U.S.-flagged barges and tugs available.  DHS has the ability to initiate a waiver to the shipping law, but the official said it is constrained by the national defense parameter.  “Right now, we do not have the authority to issue a waiver simply to make goods cost less,” he said. 