As Tesla faces several fatal crashes in the recent past that have put its Autopilot mode in scrutiny, engineers at Consumer Reports engineers have easily tricked a Tesla Model Y to drive on the electric carmaker’s driver assistance feature, without actually anyone in the driver’s seat.

During the drive, Tesla Model Y automatically steered along painted lane lines, but the system did not send out a warning that the driver’s seat was empty.

The engineers tricked Tesla vehicle by placing a small, weighted chain on the steering wheel, to simulate the weight of a driver’s hand, and slid over into the front passenger seat without opening any of the vehicle’s doors, because that would disengage Autopilot, the report said on Thursday.

Using the same steering wheel dial, the engineers reached over and was able to accelerate the vehicle from a full stop.

“In our evaluation, the system not only failed to make sure the driver was paying attention, but it also couldn’t tell if there was a driver there at all,” says Jake Fisher, CR’s senior director of auto testing, who conducted the experiment.

“Tesla is falling behind other automakers like GM and Ford that, on models with advanced driver assist systems, use technology to make sure the driver is looking at the road.”

Last week, two people were killed in a fiery Tesla crash in Texas with no one in the driver’s seat. The fatal crash is under investigation.

Harris County Precinct 4 Constable Mark Herman told Houston television station KPRC 2 that the investigation showed “no one was driving” the fully electric 2019 Tesla when the accident happened.

Tesla CEO Elon Musk tweeted earlier this week that data logs recovered from the crashed Model S “so far show Autopilot was not enabled”.

Musk argued that it would not be possible to activate Autopilot on the road where the crash took place because of the lack of “painted lane lines”.

Fisher, however, found that the Tesla car “drove up and down the half-mile lane of our track, repeatedly, never noting that no one was in the driver’s seat, never noting that there was no one touching the steering wheel, never noting there was no weight on the seat”.

“It was a bit frightening when we realised how easy it was to defeat the safeguards, which we proved were clearly insufficient,” he was quoted as saying.

There have been at least 23 Tesla Autopilot-related crashes, currently under investigation by the US National Highway Traffic Safety Administration (NHTSA).

Tesla had cautioned that Autopilot is not an autonomous driving system and requires a driver’s constant attention.