A Texas hospital is apologizing for a lapse in screening procedures that may have exposed more than 700 infants at the facility to tuberculosis.

Sometime between September 2013 and August 2014 an employee who had an active case of tuberculosis began working with infants in the nursery and in the post-partum division of Providence Memorial Hospital in El Paso, health officials said.

The city's Department of Public Health said it was working with the hospital to contact parents of the infants by telephone calls and certified letters to alert them of the possible exposure and provide instructions on getting their children tested for possible TB exposure.

The department said it received its first positive test on the employee on Aug. 27, but the hospital confirmed the employee had begun displaying symptoms as early as July.

"I want to apologize to the families that are affected by this," hospital head Eric Evans said Tuesday. "As CEO of Providence Memorial Hospital I and my colleagues take full ownership of our full role in this and making sure we get this right."

The testing of infants will continue for at least three weeks, officials said. The health department and the hospital would provide any necessary follow-up care free of charge, they said.

The infected worker is no longer employed at the hospital and is being treated for TB, a statement from Providence Memorial owner Providence Health Network said.

Tuberculosis, caused by bacteria, can spread between people through the air, although it is not considered highly contagious, requiring close contact for long periods of time before another person becomes infected.

In its active state, it can cause coughing, difficulty in breathing, and chest pain.

Latent TB, in which the bacteria are dormant in the body and cause no symptoms, is estimated to be present in 2 billion people worldwide.

"Once in the body, the bacteria usually lay dormant for months or years before they begin to grow and cause a case of active TB," the El Paso health department said in a statement. "That is why it is so important to identify people who may have been exposed, screen them, and provide treatment."

An investigation of the hospital by the Texas Department of State Health Services found "deficiencies that represent immediate jeopardy to patient health and safety," said Carrie Williams, the department's director of media relations.

"This is one of the largest TB exposure investigations we've ever been involved in, and it involves infants, so it is particularly sensitive," Williams said. "Babies are more likely than older children and adults to develop life-threatening forms of TB."