HAMDEN, Conn. (WTNH) — The cause of a massive electric bus fire is under investigation in Hamden tonight, with crews battling the flames for over 12 hours.

The electric bus was one of the first of its kind for CT Transit, but the shift to battery-powered vehicles presented unexpected challenges.

“These fires are very difficult to extinguish,” said Hamden Fire Department Battalion Chief Rich Otlowski.

Otlowski says the problem with fighting these fires stems from the lithium ion battery on an electric vehicle.

“Once they start burning, if we pour water on them, it actually exacerbates the fire, flares it up even more,” Otlowski said.

They deployed a couple of water lines to contain the flames to the bus itself, but otherwise let it burn because they didn’t want chemicals to get into the water and drain into the Quinnipiac River.

“We were concerned that any runoff would have made its way into the river resulting in environmental impact and pollution,” Otlowski said.

Fire officials say the State Department of Energy and Environmental Protection tested the water on site for contamination and found no issues, but holding off on water meant that crews were going to be out there much longer than they’re used to.

“This is a new challenge for the fire service that we are doing our best to train and prepare for,” Otlowski said.

These electric buses are also new for riders like Terry Bowden, who uses them as transportation to and from work.

They only just rolled out in the last year as a part of a multi-million dollar statewide project. As a frequent rider, Bowden has taken notice.

“It’s a smoother ride, it’s supposed to be better for the environment,” Bowden said.

As for the fire, he hopes it was an isolated incident as we continue to see more electric vehicles on the road.

“Everybody is either forced to adapt to the times or, I mean, it’s just going to happen,” Bowden said.

Two CT Transit workers exposed to the smoke were transported to the hospital, along with two firefighters for heat exhaustion. All were released following treatment. News 8 reached out to CT Transit about the fire and they didn’t want to comment, but a spokesperson said the bus involved was bought in 2021.

The incident remains under investigation by the Connecticut State Police Fire and Explosion Investigative Unit.