Northumbria Police are urging the public to 'lock out thieves' who are targeting unlocked vehicles in the north of Sunderland.
Thieves are stealing loose change, battery chargers, even wallets that have been left in vehicles that have not been locked when they've been left - including overnight.
Bikes left lying on the ground or against a wall are also being targeted.
Police are urging members of the public to be mindful of crime prevention and make sure they take measures to stop them being targeted by these opportunist thieves.
Neighbourhood Inspector Don Wade said: "Thieves are taking advantage of people leaving their vehicles unlocked, sometimes with valuable items left inside, or bikes left lying on the ground and not padlocked or secured to anything.
"It is vitally important that people take time to check they have locked their vehicle even if they are just leaving it for a few moments, thieves will actively try car doors in the hope the vehicle has been left unlocked.
"Likewise, bikes left lying on the ground or against a wall are easy targets for thieves, it literally only takes a few moments for them to ride away on it. Padlocking it to a secure post makes it much harder for thieves."
Further crime prevention advice is available on the Northumbria Police website www.northumbria.police.uk