A pair of Exxon Mobil Corp. units will pay a total of $2.4 million for allegedly breaking federal law by failing to control pollution emissions, the Justice Department said Friday.

The U.S. Department of Justice said Mobil Oil Guam and Mobil Oil Mariana Islands discharged hundreds of tons of organic compounds into the air every year from gasoline terminals on Cabras Island in Guam and the Lower Base area of Saipan. It said the businesses did not comply with pollution limits, install monitors, or submit required reports, and failed to put in some vapor pollution controls.

Bulk gasoline terminals are large storage tanks where gasoline is loaded into tank trucks so it can be distributed to storage stations. The agency said vapors can leak from storage tanks, pipes, and tank trucks as they are loaded.

The Exxon Mobil units did not place vapor controls on any loading racks at the two gasoline terminals, while 13 gasoline storage also did not have vapor controls, the Justice Department...