Hans Kristian Rausing, 49, is an heir to the TetraPak fortune his father built as a globally successful manufacturer of laminated cardboard drink containers.
Police found Eva Rausing dead at her multimillion-pound (dollar) London home on Monday. Initial post-mortem examinations Tuesday failed to establish a formal cause of her death.
The Metropolitan Police said officers arrested a 49-year-old man Monday in connection with the case. Police did not release the man's name but offered details of the arrest in response to a question about Hans Kristian Rausing.
They said they arrested the man on suspicion of drug possession, and that a subsequent search of an address in London's upmarket Belgravia neighborhood related to that arrest led to the discovery of Eva Rausing's body later that day.
Police said he remained under arrest Wednesday but was receiving medical attention at a location away from a police station. They would not say if the man was under guard.
Eva Rausing's parents, Tom and Nancy Kemeny, and the rest of her family paid tribute to a "devoted wife" and mother of four "much loved and wonderful children," saying they were devastated over her death. Their statement also alluded to her struggles.
"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," the family said in a statement. "She bravely fought her health issues for many years."
A statement from her in-laws, Hans and Marit Rausing, said they were "deeply shocked and saddened to hear of the tragic death."
Eva Rausing supported a number of charities that helped to fight addictions. One of them — Action on Addiction — was among the first to express sadness over her death and praise her "wonderfully generous" support over the years.
She also was listed as a long-time supporter of The Prince's Foundation, part of a group of nonprofit charities that have Prince Charles as their patron. His office said the prince was told of Rausing's death but did not offer further comment.
In a diplomatic scandal in 2008, Eva Rausing was arrested outside the U.S. Embassy in for reportedly trying to bring crack cocaine and heroin into building in her handbag. Police later found small amounts of cocaine, crack and heroin in a search of the couple's house. They were charged with drug possession but prosecutors later agreed to drop the charges in exchange for formal police warnings.
At the time, the Rausing family issued a statement saying relatives were "deeply saddened" by the couple's drug problems and hoped they could overcome their addictions.
Hans Rausing's Swedish father helped transform TetraPak into a hugely successful manufacturer. The fortune of the senior Rausing and his family is estimated at 4.3 billion pounds ($6.7 billion) by the Sunday Times Rich List.