Householders are being urged to be vigilant after a spate of crimes involving bogus workmen in mid-Essex.
Police recommend all householders ask callers to provide identification and a phone number, and should call the police if they are still suspicious.
The incidents in the past week have involved men claiming to be carrying out work for the council or the water authority.
Some cash and bank cards have been stolen, but other thieves have fled empty-handed after concerned residents called the police.
"We are urging householders, particularly the more trusting, elderly residents, to be on guard and go through the necessary security checks before letting any stranger over the threshold," said detective constable Paul McKee from Witham CID.
"If in doubt, call the police immediately."
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