Two chimpanzees and two orangutans have been infected at the Dehiwala Zoo, sources said.
The Zoo was allowed for only 25% of its spectator capacity with the recently relaxed travel restrictions.
However, with this situation, it is likely to be suspended the Zoo for public again.
Sources at the National Zoo say that these animals have shown some symptoms and tests revealed that Covid was infected.
Minister of State Wimalaweera Dissanayake states that it is suspected that the four animals have contracted Covid and further tests are being carried out on them.
Covid was previously infected with 11-year-old Lion Thor and 12-year-old Lioness Sheena.
Thor also developed pneumonia after being infected with the Lion Covid.
However, they later recovered.