Health officials in West Texas have begun testing some babies for tuberculosis after the revelation that more than 700 infants at an El Paso hospital were exposed to a worker found to have the disease.

The children may have been exposed at a nursery in the Providence Memorial Hospital of El Paso between September 2013 and last month, when a health care worker tested positive for TB. Local health authorities declined to say Monday how many children have come in for testing.

Armando Saldivar, spokesman for the El Paso Department of Public Health, said officials used guidelines from the Centers for Disease Control and Prevention to determine how far back to test people who could have been exposed to the disease. "We took the date of first signs and symptoms (of the health care worker) and went back three months to determine who is considered `exposed,'" he said.

Saldivar said local health officials do not know why the worker was not tested by the hospital until Aug. 21 if the person had symptoms as early as December. Also, officials are still investigating how and when the worker became infected, Saldivar said.

Audrey Garcia, Providence Memorial Hospital spokeswoman, said that so far no other workers have tested positive for active tuberculosis. She would not comment on how many results have come back or whether there were cases of latent tuberculosis. People with latent tuberculosis have the bacteria in their bodies but do not appear ill. They cannot spread the illness but may develop symptoms later on.

Carrie Williams, a spokeswoman for the Texas Department of State Health Services, said the agency previously has dealt with investigations where it was possible hundreds of people were exposed to TB, but those were in school settings, involving older children.

"This involves babies, who are more likely to develop serious disease," she said.

In a fact sheet posted on its website, the El Paso Department of Public Health says babies cannot spread the disease to family members because they lack the lung capacity to exert air, and with it the bacteria, the way adults do. Those who test positive for TB should take several anti-tuberculosis drugs between six to nine months.

Garcia said the hospital has taken actions to prevent similar incidents.

After the discovery of the infected employee, hospital regulators launched an inspection and found several violations that could threaten the hospital's Medicare funding. The Centers for Medicare & Medicaid Services has not specified what the violations were. The hospital has until Tuesday to submit a corrective plan.

Tuberculosis is at an all-time low in the U.S. with fewer than 10,000 cases in 2013, according to the CDC reports.