Atletico Madrid have confirmed two positive cases of coronavirus from testing carried out on Saturday.
Both individuals who tested positive are self-isolating at home.
Atletico are due to play RB Leipzig in the quarter-finals of the Champions League on Thursday in Lisbon.
Atletico said in a statement: “Yesterday, Saturday August 8th, all the members of the first team and of the club’s Lisbon travelling party were submitted to tests in the Ciudad Deportiva de Majadahonda as per UEFA’s protocol to participate in the Champions League quarter-finals.
“Today, two positives appeared among the known results, which are now isolated in their respective homes and were reported immediately to the Spanish and Portuguese health authorities, UEFA, the Royal Spanish Football Federation, the Portuguese Federation and the Superior Council of Sports.
“As such, a corresponding protocol planned for these circumstances has been activated, which requires new tests to be undertaken to first team players, members of the Lisbon travelling party and those who are in close contact with the positive cases, and which will result in changes in the timings of training sessions, in the structure and development of the journey and the accommodation in the Portuguese capital.
“The club will coordinate the new timings with UEFA and as soon as a new plan will be made, it will be made public. We ask for maximum respect towards the identity of the two positive cases.”
The format of the final stages of the Champions League were amended following the coronvirus pandemic with the quarter-finals, semi-finals and final all now set to be held in Lisbon, Portugal.
The remaining matches are one-legged ties played in Lisbon at Benfica’s Estadio da Luz or Sporting Lisbon’s Estadio Jose Alvalade.