The International Equestrian Federation has suspended two more athletes after their horses tested positive for banned substances.
Swiss jumper Nadja Peter Steiner and Colombian endurance rider Pablo Carreño Mora have both been provisionally banned, the governing body said.
Steiner's horse Saura De Fondcombe failed for o-desmethyltramadol, a metabolite of pain-killer tramadol.
She had been competing at an event in Tetouan in Morocco between October 5 and 8.
Carreño Mora's horse HSM Cornelio failed for ractopamine.
The substance is used to promote leanness in animals used for their meat and is banned by the FEI.
The Colombian was competing at an event in Ubate in his home country between August 19 and 20.
Both cases have now been deferred to the FEI Tribunal for a final decision, with both horses involved also provisionally suspended.
Dozens of horses and riders have now been suspended for positive tests.
A full list can be found here.