DETECTIVES still do not what killed Oxford man Denis Witney.

A dying Mr Witney was found by officers in St Clement's Street, East Oxford, on Wednesday night. A murder inquiry was launched following the 39-year-old's death in The John Radcliffe Hospital shortly afterwards.

Two men and two women - believed to be twins - were arrested on suspicion of murder in the early hours of Thursday.

Tonight a post mortem examination showed he suffered blunt trauma injuries to his head and abdomen, said police spokesman Rebecca Webber.

She added: "The post mortem was not conclusive on the cause of death. Further extensive tests will be carried out and a full report sent to the coroner in due course."

Mr Witney was homeless but had links to Headington. Miss Webber said he had not been formally identified but this was likely to happen on Monday.

Detectives have been told by magistrates they can continue to hold the suspects until the early hours of Sunday.