The babies, who were born by c-section, were tested for the new coronavirus as part of a protocol implemented by health authorities. One of the minors has symptoms.

"Two of the triplets are stable, while the third maintains a reserved prognosis with pneumonia present, which is why he is reported to be delicate but stable," said Monica Rangel, state health secretary, at a press conference.

It is the first case of multiple births of babies with covid-19, according to doctors at the hospital where the triplets were born, who consulted global records of newborns with the coronavirus.

The cases has raised scientific interest in what we know about this disease, said Miguel Ángel Lutzow, director of Health of San Luis Potosí.

The doctors who attended the delivery had no suspicion, since the mother does not have symptoms of coronavirus.

Parents are now considered as possible cases of covid-19, since they were tested and are awaiting the results.

The medical staff who cared for the mother and newborns are now in isolation and will also undergo a covid-19 test.

Pregnant women with covid-19 often have premature children, the state secretary said. Health authorities said they will investigate whether the coronavirus is transmitted through the placenta.

Mexico, with 127 million inhabitants, registered until Sunday 21,825 deaths and 180,545 cases, according to official statistics.