The Texas hospital that has become the epicenter of Ebola in the United States has apologized for mishandling the first Ebola patient diagnosed in the country and releasing incorrect information.

Thomas Eric Duncan, a Liberian man who traveled to the United States last month, sought treatment at the Texas Health Presbyterian Hospital in Dallas five days after arriving in the country. He had a fever and said he had traveled from West Africa, a region stricken by Ebola, but he was still released from the hospital hours later.

“Unfortunately, in our initial treatment of Mr. Duncan, despite our best intentions and a highly skilled medical team, we made mistakes,” Daniel Varga, chief clinical officer of Texas Health Resources, the health-care system that oversees the Dallas facility, said in a prepared statement delivered to a congressional hearing. “We did not correctly diagnose his symptoms as those of Ebola. We are deeply sorry.”

The hearing on Thursday afternoon in Washington covered the public health response to Ebola. Thomas Frieden, director of the Centers for Disease Control and Prevention, is testifying, along with Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health.

This hearing comes a day after it was revealed that a nurse who contracted Ebola while treating Duncan — the second health-care worker who was exposed to the virus that way — had traveled on a crowded commercial flight about 24 hours before she was diagnosed. In response to mounting concern, President Obama canceled a campaign trip and convened a Cabinet meeting Wednesday, while House Speaker John A. Boehner (R-Ohio) joined other lawmakers in calling for a ban on travelers from countries riven by the outbreak.

Duncan, who left Liberia on Sept. 20 and began feeling symptoms in this country later that week, was placed in isolation at the hospital Sept. 28. He was diagnosed with Ebola two days later and died last week.

But Varga said it is still not clear how two nurses — Nina Pham, who was diagnosed Sunday, and Amber Vinson, who was diagnosed early Wednesday morning — became infected while treating Duncan. Public health officials have said there was an exposure during Duncan’s treatment, pointing to those days when he was in the hospital with symptoms but had not been diagnosed with Ebola.

While Pham was following the full CDC protocols as she treated Duncan, “it’s clear there was an exposure somewhere, sometime,” Varga said. “We are poring over records and observations and doing all we can to find the answers.”

Every person who had contact with a known Ebola patient at the hospital — a number that has ranged as high as 76, according to the CDC, but could be higher now that two nurses have been diagnosed — is being actively monitored for 21 days, which includes having their temperature taken twice a day.

[This post has been updated now that Varga has spoken before the hearing.]