An employee working at Providence Memorial Hospital in El Paso, Tex., may have exposed more than 700 infants to tuberculosis.

Parents of potentially infected children received a letter from the El Paso Department of Health last week, according to ABC News. They include children born at the hospital between September 2013 and August of this year, when officials discovered that the unnamed female employee had the illness. The employee was originally identified as a nurse at the hospital. The hospital later clarified that she worked as a patient care tech.

In the letter, parents were informed that they could receive free TB screenings at the El Paso Department of Health, along with treatment.

"Your child should receive (a) TB skin test as soon as possible in order to determine if he or she has the TB germ," the letter said. "A nurse will look at the arm in 2-3 days to read the test. Your child will also need a chest X-ray so that a doctor can check to see if your children's lungs are clear. A doctor will examine your children and answer any questions you may have. If it is needed, medication will be provided to further protect your child."

The employee was placed on leave on August 16, and has not worked since, according to a statement to The Post from a hospital spokesman. Forty-three of her co-workers were also possibly exposed to TB. The El Paso Department of Health posted an exposure schedule on its Web site, presumably detailing when the employee was present in the nursery of the hospital.

According to Armando Saldivar, spokesman for the city health department, officials followed the Centers for Disease Control and Prevention's guidelines when determining how far back to test. But those guidelines suggest that the employee was symptomatic as early as December, as the AP noted, raising questions about why officials didn't test sooner.

"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,' " Salivdar told the the AP.

According to the hospital, employees are screened annually for TB. Officials assume that the employee contracted the illness after the most recent round of screenings.

At a news conference reported on by the El Paso Times, the hospital's chief medical officer, Enrique Martinez, said officials still weren't sure how the employee contracted the disease.

TB can remain latent for years, meaning that individuals will test positive for the disease but aren't symptomatic. However, those with a latent TB infection can't spread the disease to others, according to the CDC. Those who develop TB of the throat or lungs are capable of spreading it to others through coughing, speaking, or sneezing.

Infants are at a higher risk of developing TB disease after exposure, the CDC cautions, including more life-threatening forms of the illness.

Health officials told ABC that they would have test results as early as Wednesday, and that there were no positive tests as of Tuesday afternoon.

[This post has been updated]