Eva Rausing photographed in 2005

The death of Eva Rausing, one of the richest women in Britain, is being treated as "unexplained" by Scotland Yard police, who are continuing their inquiry.

Rausing, the 48-year old wife of Tetra Pak heir Hans Kristian Rausing, was found dead by police at her £20m Chelsea mansion on Monday.

It is reported that officers had been searching the property for drugs, following Mr Rausing's earlier arrest for possession of class A narcotics.

Following the discovery of his wife's body, Mr Rausing was reportedly re-arrested in connection with his wife's death. The Metropolitan Police has confirmed that a 49-year old man has been questioned by police in connection with the fatality, but has now been moved to hospital for urgent medical attention.

An initial post-mortem on Mrs Rausing's body, carried out at the Westminster mortuary, proved inconclusive. Further toxicology tests are now being carried out to establish whether drugs and alcohol were significant factors in her death.

A Metropolitan Police spokesman said: "Officers from the Homicide and Serious Crime Command are investigating, and the death continues to be treated at this time as unexplained."

The family of Mrs Rausing, who like her husband battled drug addiction for many years, said the deceased "was a devoted wife for 20 years and mother of four much loved and wonderful children. During her short lifetime she made a huge philanthropic impact, supporting a large number of charitable causes, not only financially, but using her own personal experiences.

"She bravely fought her health issues for many years. The family is devastated at her death and asks to be given privacy at this difficult time."

The couple was one of the country's wealthiest, with Hans Kristian Rausing standing to inherit the £5bn Tetra Pak business, which was established by his grandfather in 1951.