An electric bus caught on fire at a bus depot in Hamden on Saturday morning and three people were transported to the hospital to be evaluated.
Firefighters were called to the CT Transit Bus Depot on State Street after getting a report of an electric bus fire in the parking lot.
According to fire officials, lithium ion battery fires are difficult to extinguish due to the thermal chemical process that produces great heat and continually reignites.
With this type of fire, officials said they have to let it burn because it can't be extinguished.
At the scene, crews said they were able to protect other exposures.
Investigators said two CT Transit workers were taken to the hospital as a precaution from exposure to the smoke. One firefighter was also transported to the hospital for heat exhaustion.
The fire marshal is investigating the incident.