A police investigation was under way today after the death of a middle-aged woman from a suspected drugs overdose the fourth in Oxfordshire in three months, writes Paul Warner.

Tessa Coleman, 38, of New Cross Road, Headington, Oxford, died on Friday, 24 hours after being admitted to the John Radcliffe Hospital. A police spokesman said a man had been arrested on suspicion of supplying controlled drugs. The man, who has not been named, was released on police bail after being interviewed over the weekend.

Acting Det Insp Andrew Murray said: "We are investigating the death. The cause is unknown at the moment." Police put out a warning about a killer batch of heroin after Nicola Horne, 20, and Nicholas Byrne, 24, of Middleton Road, Banbury, died last month from suspected overdoses.

It is believed the drug was extremely powerful or contaminated.

Nathan Cox, 16, of Southmoor, died three months ago at a house in Abingdon from a suspected heroin overdose.