Hans Rausing, one of the richest men in Britain and heir to the Tetra Pak drinks carton empire, has been arrested in connection with his wife's death after her body was found at their home in Chelsea in west London.
Her death was being treated as unexplained.
Mr Rausing had earlier been detained by police on suspicion of possessing drugs.
More top news
Warmer with a mild, muggy night ahead
The headteacher of Saffie Rose Roussos's primary school has paid tribute to the little girl who was "beautiful in every sense of the word".
Ten people have died on the mountain so far this climbing season - four more than mountaineering officials expect in a typical year.