In 2018 there were about 181,500 highway vehicle fires, according to the National Fire Protection Association. The vast majority of those were gasoline and diesel-powered vehicles. For whatever reason, we expect and accept that. But with EV fires it's different.
The National Traffic Safety Board addressed these EV fires in January with a report noting that there are two main safety issues. First, the inadequacy of vehicle manufacturers' emergency response guides, and the gaps in safety standards and research related to high-voltage lithium-ion batteries involved in high-sped, high-severity crashes.
Additionally, EVs pose a risk of electric shock to emergency responders, and then there's the thermal runaway problem. That is a process that is accelerated by increased temperatures, in turn releasing energy that further increase temperature. It's an uncontrolled positive feedback loop.