LAUSANNE, Switzerland - The IOC issued a stern statement on Tuesday promising to step up the fight against sports doping after a series of damning reports exposed systematic and mass cheating by Russian athletes.
The Olympics organizers said 31 athletes in six sports have tested positive in reanalysis of their doping samples from the 2008 Beijing Olympics.
The International Olympic Committee said it has opened disciplinary proceedings against the unidentified athletes from 12 countries.
The samples had been stored at the IOC laboratory in Lausanne. They were retested using enhanced methods on athletes who were expecting to compete at the Olympics in Rio de Janeiro in August.
The IOC said "all those athletes infringing anti-doping rules will be banned from competing" in Rio.
The committee said the results of 250 retests from the 2012 London Olympics will "come shortly." There will also undertake a "wider retesting" of medalists from Beijing and London.
"The re-tests from Beijing and London and the measures we are taking following the worrying allegations against the Laboratory in Sochi are another major step to protect the clean athletes irrespective of any sport or any nation. We keep samples for ten years so that the cheats know that they can never rest," IOC President Thomas Bach said in the statement.
Over the weekend, Russia's sports minister said his country has a "problem" with doping and is "very sorry" that its cheating athletes were not caught sooner.
"Serious mistakes have been made by the federation management, along with athletes and coaches who have broken anti-doping rules and neglected the principle of fair play," said Vitaly Mutko, writing in British newspaper The Sunday Times. "Let us be clear. We are ashamed of them."
Russia will discover on June 17 whether its athletics federation has met the reform criteria to return to competition in time for the Rio de Janeiro Olympics.
Russia was plunged into another doping scandal last week after a series of exposes by "60 Minutes," The New York Times, and others.
A former Russian anti-doping official allowed "60 Minutes" to listen to 15 hours of conversations he secretly recorded with a prominent doctor involved in the country's testing regime.
Dr. Grigory Rodchenkov shared details of a systematic cover-up in Sochi during Skype conversations with Vitaly Stepanov, a former Russian anti-doping official turned key whistleblower. The doping program reportedly involved at least 15 Russian medal winners.
"He had the ability to help to get the necessary results," Stepanov told CBS News -- referring to gold medals.
In the recordings, Rodchenkov named Russian gold medalists in three sports -- bobsled, skeleton and cross country skiing -- whose dirty drugs tests he helped cover up.
It was all part, he said, of an elaborate scheme to protect Russia's Olympic medal winners, with the help of his country's intelligence service, known as the FSB.
"FSB tried to control every single step of the anti-doping process in Sochi," Stepanov said Rodchenkov told him.
The FSB figured out a way to open bottles considered to be tamper-proof containing urine from drug-tainted athletes. Then they filled the bottles with clean urine collected from athletes before they started doping.
Rodchenkov said he then had two weeks after the Sochi games -- to make sure, in his words, people turned out to be clean before test samples were sent to the International Olympic Committee in Switzerland for storage.
CBS News also learned a recent review of blood tests in at least one Olympic event at Sochi has revealed evidence of test tampering involving Russian athletes.