Thames Valley Police are re-investigating the deaths of eight people dating back to the 1970s.
Cold case detectives say the deaths - which occured in Berkshire, Oxfordshire, and Buckinghamshire - are unrelated.
The operation, named Nightingale, has been established as police have previously been unable to identify the bodies in each case.
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There is a high risk from birch pollen during any good weather. Oak pollen is also on the increase.
Wednesday's weather for the west of the region
Wednesday's weather for the east of the region