A married couple arrested on suspicion of murdering elderly residents at a care home in the south west of England are now being investigated in connection with 12 deaths.

Avon and Somerset Police had previously said it was looking into five "suspicious'' deaths of residents at Parkfields Residential Home in Butleigh, Somerset.

Registered nurse Rachel Baker (46) and her husband Leigh (50) were initially questioned following the death of 97-year-old resident Lucy Cox on New Year's Day 2007.

Mrs Baker was arrested on January 5 on suspicion of administering a noxious substance and Mr Baker, a chef, was arrested two days later.

In December 2007, the couple were arrested on suspicion of murdering four women residents -- Mrs Cox, Nellie Pickford (89), Marion Alder (79) and one other woman -- and a man, Fred Green (81).

Avon and Somerset Police refused to give any details of the seven additional suspicious deaths yesterday but detectives confirmed they had exhumed the remains of three other former residents in order to carry out toxicology tests to establish whether they had been poisoned.

Mr and Mrs Baker, who had managed the care home for more than a decade before it was closed last year, live in Glastonbury with their six-year-old daughter. They are also suspected of theft and unlawful possession of controlled prescribed drugs and attempting to pervert the course of justice.

Police confirmed yesterday, the Bakers' bail period was being extended to January 2009 while investigations continue.

The private home, which housed up to 20 elderly residents in flats and bungalows, was owned by Mr Baker's parents, June and Malcolm, but had been managed by his wife, Rachel, since 1988.