In a book of confessions, Riis revealed how during the 1998 Tour de France he threw phials of EPO (erythropoietin) down the toilet after hearing that his Deutsche Telekom team would also be searched as part of the probe into the Festina doping scandal.
"In my room I didn't have a choice. My phials of doping products had to disappear quickly. In just a few minutes I gathered all my doses of EPO and threw them down the toilet," explained Riis.
Tour de France organisers in 2007 stripped Riis of his 1996 title after he admitted to doping when he won the race.
Saxo Bank team director Riis also admitted spending up to one million Danish Kroner (134,000 euros) on doping products.
"Doping products must have cost me between half a million and a million Kroner (67,000 to 134,000 euros today)," Riis told the daily Politiken.
Riis and his wife Anne Dorte told the weekly freesheet Soendagsavisen how doping became natural in their household with EPO being stored in the fridge in their kitchen.