Police officers in forensic evidence suits could be seen at a house in Headington.
*UPDATE*: A man in his 30s has been found dead
The emergency services were said by neighbours to have been at the property in Bateman Street from before 6pm.
At 8pm, two detectives and two uniformed officers were waiting outside the house.
The plain clothes officers were seen walking back towards an unmarked Corsa carrying a large clear plastic evidence bag.
One neighbour said: "I was walking home and saw two police cars and a few police officers milling around."
Thames Valley Police has been approached for comment.
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