ATLANTA (AP) — A town south of Atlanta advised its residents on Friday not to drink their tap water after a fuel spill at Atlanta’s airport may have contaminated the Flint River.

The city of Griffin, whose water system serves more than 20,000 customers, said water might not be safe to drink even if it was boiled and asked people to use bottled water instead for drinking, cooking or brushing teeth.

Alnissa Ruiz-Craig, a spokesperson for Hartsfield-Jackson Atlanta International Airport, said the fuel spill happened Friday morning and that cleanup was underway. She couldn’t say how much fuel escaped or why.

Griffin officials said they shut down water intakes from the Flint as a precaution, even though they didn’t believe the contaminated water reached the city. The Flint originates near the airport, with much of its headwaters hidden in pipes flowing under the sprawling airfield, before flowing southwest and becoming one of Georgia’s major rivers on the way to merging into the Apalachicola River in Florida.

Jet fuel and sewage spills from the airport have repeatedly contaminated the Flint headwaters.

Griffin officials said they are now using drinking water from an unaffected reservoir in nearby Pike County and opened fire hydrants to flush the water system. The city is testing its water to determine whether it’s safe.