Twenty-eight athletes who competed at the 2005 and 2007 World Championships have returned “adverse findings” from retested samples, the International Association of Athletics Federations (IAAF) has said.
According to the world governing body, a large majority of the athletes are retired with “very few” still active.
In total, there were 32 adverse findings from the 28 athletes.
“The IAAF is provisionally suspending them,” it said in a statement.
The IAAF added that none of the athletes concerned would be competing at the 2015 World Championships in Beijing, which get under way on August 22.
None of the 28 can be named yet “due to the legal process”.
The 2005 World Championships took place in Helsinki, Finland, with Japanese city Osaka hosting the event two years later.
More to follow.