Motorists are being urged to be on their guard after what police have described as an 'organised' spate of vehicle crime.
Police have urged car owners in Teignbridge to clean out their cars after the wave of vehicle-related crime.
And it is thought that travelling criminals may be coming from outside the district to raid cars.
They are also targeting people who are parking their cars and hiding valuables before heading out for a walk on Dartmoor.
Teignbridge senior officer, operations inspector Ian Curson said: "Empty your car. It's not worth the risk."
Police have been battling escalating car crime over the last few months and have reiterated their calls for motorists to take extra care when leaving their vehicles overnight.
Insp Curson said: "There has been an increase in vehicle crime in the last couple of weeks.
"On one occasion five cars were broken into in Heather Close, Teignmouth, but only one car had items stolen from it.
"On another night four cars were hit in Bishopsteignton.
"It appears whoever is doing it is travelling into the area and targeting smaller outlying areas which do not have the CCTV or police presence larger, more urban areas have.
"They are stealing anything they can find, or even what looks like it is of value.
"If someone has a plastic bag concealed under a seat which has absolutely nothing of value in it the car will be broken into just so the offender can see if it has anything in it.
"The message from us is quite simple: take everything out the car, even leave the glove box open if you have to, to show there is nothing in there."
Insp Curson said criminals also have 'spotters' who watch car parks, particularly on Dartmoor, and swoop on cars which have sat navs, cameras or handbags left in them.
He said: "The average person has an insurance excess of £250. If you add to that the loss of any valuables and the feeling of vulnerability, leaving goods in the car is just not worth the risk."
Teignmouth inspector Chris Shaw said: "It really is a problem and some people are still leaving cars unlocked.
"We can play our part but the public needs to do their bit too."
Police are carrying out a range of anti-crime measures across Teignbridge to raise awareness of the issue, including Moorwatch Action Days, the first of which is on Tuesday.
Fran Bennett, Teignbridge's crime reduction officer, said: "The days cover the whole moor and look at a range of crime prevention measures, including securing outbuildings, but with a focus on vehicle related crime.
"We will be leafleting cars, going from address to address and spreading the crime prevention message.
"People are leaving a lot of their goods in cars and we want to make sure people are aware of the problem.
"We would urge them not to leave valuable goods in their cars. Ideally anything like a sat nav will be hidden out of sight before they park up so they don't fall victim to those who have gone to these areas specifically to target cars."