WASHINGTON — The U.S. Customs Service has quadrupled the number of lines of its NAFTA facsimile service to aid businesses calling in with questions, it said Friday.

Companies with inquiries about tariffs, rules of origin or other complexities of the North American Free Trade Agreement can call the Customs Service and choose from among 200 issues listed on a menu. Customs will then fax the information to the company free of charge, an agency spokesman said.

The fax system has been getting 250 calls per day, while agency staffers are handling about 500 daily queries, the agency said. Sixteen fax lines are now in place, up from four.

Importers can reach the NAFTA FlashFAX service at (202) 927-1697.