FREDERICK, Md. (AP) — Frederick County’s public transit agency says it has returned its fleet of electric buses to service after checking for a flaw that caused a fire in the lithium-ion battery compartment of one of the vehicles.

Spokeswoman Kendall Tiffany said in a statement Monday that investigators concluded the Sept. 27 fire in Frederick was caused by overheating from a cable connection that was not properly crimped. The bus was not carrying passengers, and nobody was hurt.

Tiffany says the damaged bus will be repaired at no cost by Complete Coach Works of Riverside, California.

She says the four other buses have been checked for proper electrical connections and returned to service.

Lithium-ion batteries have been linked to fires in some smartphones and hoverboards, and aboard several cargo jets.