Mexico's public health system has suspended administrating vaccines across the country after two babies died and 29 others fell ill in southern Mexico.

The cause of the deaths and other adverse affects are unknown, but officials with the Mexican Institute for Social Security said they have launched an investigation.

At least six of the 29 babies that were sickened are seriously ill, after receiving vaccinations for tuberculosis, rotavirus, and Hepatitis B, according to a statement from the Mexican Institute for Social Security. Children usually receive these vaccines before they are six months old.

Mexican Institute for Social Security said on Saturday it had stopped giving vaccines nationwide as a precaution.

A Roman Catholic priest, Rev. Marcelo Perez, told the Associated Press that the babies fell ill within hours of receiving the vaccines.