Burglars raided Cottenham High Street post office on Monday.
They caused more than £1,000 worth of damage and stole two cash cassettes from an ATM machine but neither contained any money.
A door was forced open by two of the three offenders who are believed to have used a black Audi car.
One was described as wearing a grey hooded top. The vehicle made off in the direction of Cambridge.
PC James Swann, investigating, said: “I am keen to speak to anyone who has any information about this burglary and would urge anyone who was in the area at the time to get in touch.”
If you have information call PC Swann on 101 or Crimestoppers, anonymously, on 0800 555111.
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