The Federal Transit Administration has issued an alert to transit agencies that a safety defect is creating a fire risk. 

The advisory issued Wednesday covers about 483 battery-electric buses that were produced by Proterra from 2019 to 2022. On Sept. 5, the National Highway Traffic Safety Administration issued a recall on the vehicles. 

According to the safety recall report, a Proterra bus began to smoke in July 2021 due to an issue with the charging connector. A fleet check was conducted in August 2021, and the investigation found a dozen buses whose connectors showed similar issues. 

A software update was issued in March 2022, but then a second smoke incident was reported in Miami on Jan. 15, 2024, which was found to be a software issue. Then, in August, there was another “thermal incident,” according to the report, and a voluntary recall was issued on Aug. 29. 

Customers who purchased Proterra, which went bankrupt in August 2023, have reported a number of issues, including difficulty getting parts for repairs. In many cases, the buses remain inoperable for weeks. Phoenix Motorcars acquired Proterra’s transit bus division after the bankruptcy.