Sheikh Ali al-Thani and Bassem Mohammed both tested positive for carboxy-THC, a metabolite of cannabis, the International Equestrian Federation (FEI) said.

They had been competing at the Olympic jumping qualifier for the Middle East and Africa in Morocco's capital Rabat in October, where they helped Qatar book one of two Tokyo 2020 places available in the team competition. 

Neither have been provisionally suspended by the FEI as carboxy-THC is only a specified substance on the 2019 World Anti-Doping Agency (WADA) banned list.

These are substances which WADA says can enter an athlete's body inadvertently, which could allow for more flexibility in any sanctions.

However, carboxy-THC is banned under the FEI's rules for human athletes.

Should the governing body find the pair guilty of a doping offence, Qatar could lose their Tokyo 2020 place with Morocco next in line to replace them.

Sheikh Ali competed at the Rio 2016 Olympics in the individual jumping event, finishing sixth.

He also carried Qatar's flag at the Opening Ceremony.

Bassem finished in joint 28th place, with the pair then helping Qatar to ninth in the team jumping.

Egypt also qualified for Tokyo 2020 at the event in Rabat.

"In order to maintain the integrity of the ongoing legal process, the FEI will not comment further on these cases at this time," the governing body said.

Canada's team has already lost their Tokyo 2020 jumping place after rider Nicole Walker failed a drugs test for benzoylecgonine, a metabolite of cocaine.

She reportedly tested positive after drinking coca tea, with the decision being appealed. 

Countries which do not qualify for the team event can only select one rider for the individual competition.