WASHINGTON - To help reduce the risk of fires, air travelers will no longer be able to pack loose lithium batteries in checked luggage beginning Jan. 1, the Transportation Department said yesterday.

Passengers can still check baggage with lithium batteries if the batteries are installed in electronic devices, such as cameras, cell phones and laptops. If packed in plastic bags, batteries may be in carry-on baggage. The limit is two batteries per passenger.

The ban affects shipments of nonrechargeable lithium batteries.

The National Transportation Safety Board this month said it could not rule out lithium batteries as the source of a cargo plane fire at Philadelphia International Airport last year.