Mexico's public health system has mounted an investigation after two babies died and 29 were sickened in an impoverished community in southern Mexico.

Six of the 29 babies are in grave condition after receiving vaccinations for tuberculosis, rotovirus and Hepatitis B, which are generally administered between 0 and 6 months, according to a national schedule.

The cause of the adverse reactions is not known, the Mexican Institute for Social Security said Sunday.

The 23 other babies are in stable condition, according to the institute.

Officials: José Antonio González Anaya, the general director of the Mexican Institute for Social Security (far right), and Manuel Velasco Coello, the governor of Chiapas, were photographed meeting with affected families

Concerns: Six of the 29 babies are in grave condition after receiving vaccinations for tuberculosis, rotovirus and Hepatitis B, which are generally administered between 0 and 6 months, according to a national schedule

The institute said it stopped vaccines nationwide on Saturday as a precaution.

On Sunday, the Mexican Institute for Social Security said that just Hepatitis B vaccine lots have been stopped in Simojovel, Chiapas.

CNN has reported that officials are looking into whether bacteria or a virus are culprits, along with needles.

The Rev. Marcelo Perez, a Roman Catholic priest, told The Associated Press that families of the babies said they became sick within hours.

The adverse reactions started Friday and the babies were being treated in a hospital in Simojovel, Chiapas, where 93 percent of the people live in poverty, 69 percent in extreme poverty, according to government statistics

The institute said Saturday that 52 children received the vaccines on Friday.

The hospital 'doesn't have adequate personnel or equipment,' Perez said. 'The real problem is the terrible conditions we have ... so that when a baby comes in with convulsions, he leaves dead.'

The institute in a news release said that both José Antonio González Anaya, its general director, and Manuel Velasco Coello, the governor of Chiapas, have met with the affected families.

Officials have said the children are being treated in Tuxtla Gutiérrez, Chiapas.

The federal and state government, in a statement Sunday, promised the best medical care for the babies and to stay in contact with the parents to answer all their questions.

Perez said he was helping the families collect all the information that could help officials discover the cause of the adverse reactions.

The federal and state government, in a statement Sunday, promised the best medical care for the babies and to stay in contact with the parents to answer all their questions