The incident was reported around 10:40 a.m. at Durfee Avenue and Rosemead Boulevard, according to the Los Angeles County Fire Department.
Ten minutes after that, another car reportedly drove over the embankment, but additional details about either incident were limited.
Video from the scene showed a black Honda and a white Tesla down in the riverbed along the rain-soaked road.
Three people were injured, but officials could not specify whether those individuals were patrons of the food stand or inside the cars that crashed.