Police have issued a warning after four high-value cars were stolen from driveways in a town during one night.
A Mercedes and three BMWs were taken from outside homes in Bushey in Hertfordshire between Thursday night and Friday morning.
Hertfordshire Police said special devices were used to intercept key fob signals from inside the home to then unlock and start the vehicles.
It urged drivers of keyless cars to store fobs in signal-blocking pouches.
The force said it was seeing an increase in vehicle thefts across the county and had increased night-time patrols.
Cars were taken from Merry Hill Road, Wren Crescent and two from separate properties in Coldharbour Lane in Bushey.
Insp Rachael Robertson said: "Using a signal blocking fob pouch, such as a Faraday Bag, or storing your fob in a metal box will help prevent the signal from being detected.
"You can also turn off wireless signals from your fob when it is not being used."
She also advised drivers to consider using a steering-wheel lock and reminded buyers of second-hand keyless cars to remember to re-programme their fobs.
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