CHAMBLEE, Ga. (AP) — More than 1,000 gas stations in the Southeast reported running out of fuel, primarily because of what analysts say is unwarranted panic-buying among drivers, as the shutdown of a major pipeline by a gang of hackers entered its fifth day Tuesday.

Government officials acted swiftly to waive safety and environmental rules to speed the delivery of fuel by truck, ship or rail to motorists and airports, even as they sought to assure the public that there was no cause for alarm.

The Colonial Pipeline, the biggest fuel pipeline in the U.S., delivering about 45% of what is consumed...