Nepal, Sept. 14 -- Early Friday morning, in Bharatpur, a 55-year-old former school director lost his life inside a burning electric car while driving home. By the time firefighters reached him, there was nothing left to save. What remained was a wrecked car, a grieving family, and a country suddenly unsure whether the electric vehicles now filling its roads and showrooms are safe to drive.

Investigators have not yet determined why the car caught fire. It may prove to be a fault in the charging system, a mechanical failure unrelated to the battery, damage from a prior collision, or a battery fire-several plausible explanations that experts have declined to rule in or out before the forensic work is done. That restraint in drawing a conclu...