Imagine a secret tunnel beneath the city of Los Angeles where a crew of thieves hide stolen cars. Beneath the concrete, they’re safe from any tracking devices installed in the vehicles. There, they can take their time disassembling and parting out their loot. Sound like some Hollywood heist movie? One whistleblower claims it’s “plain fact.”

The U.S. Army Corps of Engineers built Whittier Narrows Dam in Montebello, California, to manage runoff from the San Gabriel River. When the concrete channel isn’t flooded, you can drive along it and access tunnels flowing to the Rio Hondo. A whistleblower who works along the dam told Fox 11 News that a “band of brothers” uses the area to stash and disassemble stolen vehicles.

He shared photos showing several abandoned work trucks he claims these thieves parted out. They steal fresh vehicles “on average, at least once a week.”

There may be a good reason to hide stolen cars in a tunnel

Why bother with a half-flooded tunnel? “They come into the channel and they hide because they know that whether the car has LoJack or not, or some sort of a GPS tracker on it. Once it’s underneath three feet of concrete or soil, the signal is lost.”

He adds the thieves form a “group in which they work with each other to they barter and trade in stolen goods.”

The story seems far-fetched. But just two weeks ago, news helicopters recorded a man in a stolen truck using this exact tunnel to escape a police chase. This anonymous source calls the dramatic incident “just another business day for them (the thieves).” You can hear the whistleblower interviewed in the video below: