Nguyen Quang Tung parked his car in front of house No. 315 on Vong Street of Hai Ba Trung District on Thursday. When he returned and tried to start his car using a smart key, he failed.
After over 10 minutes of unsuccessful attempts, he decided to change the remote's batteries.
"But I still couldn't enter the car, so I intended to have a vehicle take my car away for repair. But after I tried my mechanical key, the door unlocked normally," he said.
Several businesses in the area have also been affected by the strange phenomenon.
Le Dinh Hieu, a café owner on Vong Street, said all of his customers who have vehicles with smart keys could not start their vehicles as they tried to leave.
After an investigation revealed that it was only happening at the Nguyen An Ninh-Vong intersection, the café told its customers not to lock their vehicles upon parking.
"But many people worried about safety, and some locked their vehicles out of habit, so they had to walk their vehicles away for over 10 m," he said.
The phenomenon apparently affected a 100-meter section and lasted 10 days. Only smart keys were affected, while mobile and Wi-Fi signals operated normally.
Authorities of Dong Tam Street enlisted the help of the Authority of Radio Frequency Management under the Ministry of Information and Communications, along with Hanoi police, to investigate.
After using devices to detect electromagnetic radio frequencies in the area on Thursday, the units discovered the source of the signal disruption: a remote device used to operate water pumps belonging to a family on Vong Street.
The device, which had no clear origin, did not satisfy wave frequency standards. After turning it off, the smart keys functioned normally.