Belinda Bencic and Ons Jabeur have both tested positive for Covid-19 after playing in Abu Dhabi.
They are the third and fourth players to have returned positive tests after travelling to the Mubadala World Tennis Championship.
Britain's US Open champion and the 2021 BBC Sports Personality of the Year winner Emma Raducanu withdrew before the start of the tournament.
Rafael Nadal revealed he had tested positive upon his return to Spain.
On Tuesday, his coach Carlos Moya said he had also returned a positive test.
Switzerland's Olympic champion Bencic lost to Tunisia's Jabeur in the sole women's match at the championship.