Angela Smith, 28, a mother of two, was found dead in a cell at a police station in Edinburgh early on Sunday morning after a Saturday night drugs raid at her flat.

A spokesman for Lothian and Borders Police said an investigation was under way.

"We don't want to elaborate on the details. There is a strict protocol to follow and there are pretty tight regulations governing what can be said at this stage because there will have to be an inquiry."

A neighbour who lives in the same block as Ms Smith in Southhouse Square said: "The police barged into the flat on Saturday night and we could see two young men and a woman getting taken out. There is a lot of drug-dealing round here and no-one really knows who their neighbours are. Angela's mother is looking after her two kids now."

Ms Smith was taken to St Leonard's police station, one of only a few which has nurses based in its custody suite. Lothian and Borders Police is the only force in Scotland to operate the system, which began in April 2006, employing two nurses on 12-hour shifts in the evenings and weekends.

Iain Whyte, the convener of Lothian and Borders police board, said: "This is a tragic case and we are awaiting the outcome of the investigation. It is far too early to make a judgment at this stage.

"The custody nurses were put in to ensure any medical
conditions were monitored. Not every system is foolproof, but we would hope that it would help."

John Scott, the chairman of the Howard League for Penal Reform in Scotland, said it was vital that sufficient resources were allocated for monitoring prisoners in police custody.

"It's an area we need to keep constantly under review. With the pressure of work and lack of resources for both police and nursing staff, it is very easy for things to be missed.

"There was a recent case south of the Border where someone who was very drunk was brought into a busy police station, but where officers didn't realise he had a head injury. The answer would seem to be for the bigger stations to have nurses on site. But there can be problems with the sheer numbers being processed due to drink and drugs.

"However, it could have been that in the case at the weekend the woman was seen by a nurse."