The US National Transportation Safety Board is investigating a Tesla (TSLA.US) crash in California that resulted in a fire.

The National Transportation Safety Board said Wednesday night it was investigating a crash and fire involving a Tesla (TSLA.US) semi-truck on a California highway. The agency said it would work with the California Highway Patrol on a safety investigation.

The automaker and the California Highway Patrol did not immediately respond to requests for comment.

A Tesla semi-truck caught fire and crashed on a northern California highway near Emigrant Gap early Monday morning, closing a highway for more than an hour and causing no injuries.

Tesla makes its semi-trucks at a factory near Reno, Nevada, and uses 8-wheel trailers to transport parts to its factory in the San Francisco Bay Area. The semi-truck, which debuted in November 2017, is still in a “production” phase seven years later.

While electric vehicle fires are less common than gasoline vehicle fires, they can be more dangerous because of the risk of lithium-ion batteries catching fire, which can take a long time and a lot of effort to safely extinguish. Experts say that electric vehicle fires burn differently than gasoline vehicle fires, typically lasting longer and having a tendency to reignite.

Tesla’s semi-trucks are equipped with especially large batteries for long-haul use. Official numbers have not been released, but according to energy consumption data, the battery capacity of the 500-mile version of the semi is estimated to be around 850-900 kilowatt-hours (kWh). A typical electric vehicle or crossover typically has a battery capacity of 75-85 kWh, while a pickup truck ranges from 123 kWh to 205 kWh. So, by comparison, the 900 kWh battery is huge.