Alan Ruck‘s car crash last week is still a mystery in terms of cause — but cops do have a theory they’re running with for now … they think technology got the better of a human.

Law enforcement sources tell TMZ … investigators believe they know what caused the “Succession” star’s wreck at a pizza parlor in Hollywood, and from the sounds of it — the police are buying Alan’s story here.

Our sources say Alan told officers he simply didn’t know what caused the accident.

We’re told those who were on the scene believed him — as they saw no evidence he was under the influence, distracted or otherwise impaired during the accident … so, as far as they’re concerned, they believe it was, in fact, just an accident.

Our sources also tell us the LAPD thinks this was just a mishap arising from the fact that Alan’s truck, a Rivian R1T, is brand-spanking new and super high-tech.

Indeed, it is an electric truck … and it certainly looks fancy from the inside out. It also features three all-wheel drive systems — Dual Motor, Performance Dual-Motor and Quad-Motor … and depending on which one you’re on, it can go from 0-60 MPH reeeal fast.

We have no idea if or how any of this played a part in Alan’s sitch — but it sounds like the police think he might’ve just been in over his head handling this machine … and that it just got away from him. As a result, we’re told they’re closing the book on this case … and leaving it to insurance.