Canoe sprint teams from Romania and Belarus have been banned for a year for systemic doping.
The sanction, handed out by the International Canoe Federation (ICF), means both squads will miss next month's Olympic Games in Rio.
According to the governing body, the ban proved a "zero tolerance" approach and removed Olympic places from "cheats".
Mass drug test failures among canoeists from both countries were reported in June, with the ICF provisionally suspending all involved.
The year-long bans follow new evidence being heard at an Executive Board meeting in Polish city Krakow, with the majority of the cases involving controversial heart attack drug meldonium.
“This is a clear message that the ICF has a zero-tolerance stance to cheats and that we will do everything within our powers to remove them from our sport," said ICF President Jose Perurena.
“I am disappointed that we have reached this point, but I am sure our swift actions will act as a strong deterrent and underline that we support clean competition and nothing else will be tolerated.
"Our athletes need to be assured that they are racing as equals.”
The drug failures came after out-of-competition testing in April, with Belarus even facing a criminal investigation with the French police probing the matter.
Sanctions for individual canoeists will be decided in the coming weeks.
The Romanian Olympic and Sports Committee confirmed in June that C1 entrant Leonid Carp and C2 partner Ştefan Strat had failed for meldonium, along with women's K2 paddler Elena Meroniac, a silver medallist at the Baku 2015 European Games.
The entire world champion C4 1000 metre quartet of Traian Neagu, Catalin Turceag, Daniel Burciu and Petrus Gavrila also failed, with all seven due to compete in Rio.
French newspaper Le Monde reported that five members of the Belarus canoe sprint team had failed for meldonium, including brothers Andrei and Aliaksandr Bahdanovich, the C2 1000m Olympic champions at Beijing who won silver four years later in London.
They were each reportedly caught in France following a surprise visit during a training camp by testers led by former cyclist Christophe Bassons.
The ICF will now reallocate their Rio 2016 quota places to other countries, and will confirm its final list of athletes before Monday's deadline.
Even tougher sanctions for Romania and Belarus are possible should more evidence emerge.
Meldonium, however, has proved tricky for numerous Federations since it was banned by the World Anti-Doping Agency (WADA) from January 1.
Question marks over how long the endurance-booster stays in the human body has been a major stumbling block, with WADA twice forced to issue new guidance.
That has seen some athletes have suspensions from competition lifted with WADA the subject of much criticism.
The organisation admitted that "limited data exists to date" on the urinary excretion of the drug while the renal elimination is said to "vary significantly between individuals".
Elsewhere, the ICF has also confirmed that four as-yet unnamed Kazakhstan athletes have been banned for two years each after submitting positive tests for methasterone, an oral anabolic steroid.
The substance was taken as part of a nutritional supplement, underlining "the need for all athletes to be especially vigilant when consuming supplements" according to the ICF.