Major League Soccer (MLS) confirmed the two results in question came from players, while everyone on both teams has since been retested.
But because the results of the second tests – which took place on Sunday morning in Orlando, where the MLS is Back competition is being hosted – are not expected before the initially scheduled kick-off time, the league was left with no option but to postpone the contest.
An MLS statement read: "Major League Soccer announced that today's DC United vs Toronto FC match has been postponed and will be rescheduled. MLS will announce details later today [Sunday] for the rescheduled match.
"Under the league's health and safety protocols, clubs are tested the day before each match. The results of yesterday's tests for D.C. United and Toronto FC produced an initial unconfirmed positive COVID-19 case for one player and an inconclusive test for another player.
"Because of the arrival time of the clubs in Orlando, the league's protocol called for retesting both teams this morning and to await the results of those tests prior to playing the match.
"Major League Soccer will continue to prioritize the health and safety of all participants of the MLS is Back tournament in making these decisions."