American sprinter Deajah Stevens and Kenyan road runner Alex Korio Oliotiptip have been provisionally suspended for whereabouts failures by the Athletics Integrity Unit (AIU).
Stevens and Oliotiptip are among the four athletes to have been given provisional suspensions by the AIU, which handles doping cases for World Athletics.
Gabrielle Thomas, also of the United States, has also been handed a provisional ban for whereabouts failures, while Oliotiptip's compatriot Mikel Kiprotich Mutai has tested positive for a prohibited substance.
The provisional suspensions given to Oliotiptip, who ran as a pacer for Eliud Kipchoge when he broke the two-hour marathon barrier last year, and Mutai add to Kenya's doping woes.
Nearly 50 Kenyan athletes are currently serving suspensions, according to the AIU database.
Stevens, who finished seventh in the 200 metres final at the 2016 Olympic Games in Rio de Janeiro and was fifth at the following year's World Championships in London, amassed three whereabouts violations in a year and is facing a ban of up to two years.
Oliotiptip, a sub 59-minute runner in the half marathon who came 11th in the 10,000m at last year's World Championships, and Thomas are accused of committing the same violations.
Thomas, who claimed the 200m National Collegiate Athletic Association title in 2018 and is a two-time winner of the event at the Lausanne Diamond League, has denied any wrongdoing and said she expects to be cleared of failing to make herself available for anti-doping tests.
"Phone tracking data and multiple witnesses will conclusively show that I was at the exact location I established in my whereabouts and that the doping control officer simply failed to locate me and failed to follow proper protocol."
World 100m champion Christian Coleman was cleared last year of a whereabouts charge after one of the American's alleged violations was backdated.