Washington, May 1 -- U.S. government searches of travelers' cellphones and laptops at airports and border crossings nearly quadrupled since 2015 and were being done for reasons beyond customs and immigration enforcement, according to papers filed Tuesday in a federal lawsuit that claims scouring the electronic devices without a warrant is unconstitutional.

The government has vigorously defended the searches, which rose to 33,295 in fiscal 2018, as a critical tool to protect America. But the newly filed documents claim the scope of the warrantless searches has expanded to assist in enforcement of tax, bankruptcy, environmental and consumer protection laws, gather intelligence and advance criminal investigations.

Agents with U.S. Customs ...