In this March 14, 2020 photo provided by Elizabeth Pulvermacher, travelers returning from Madrid wait in a coronavirus screening line at Chicago's O'Hare International Airport. (Elizabeth Pulvermacher via AP)

CHICAGO (AP) -- Harsh criticism rained on the Trump administration Sunday from state and local officials over long lines of returning international passengers at some U.S. airports that could have turned them into coronavirus carriers as they tried to get home.

Illinois Gov. J.B. Pritzker and Chicago Mayor Lori Lightfoot, both Democrats, lambasted the administration for allowing about 3,000 Americans returning from Europe to be stuck for hours inside the customs area at O'Hare International Airport on Saturday, violating federal recommendations from the Centers for Disease Control and Prevention that people practice "social distancing."

The passengers, many of them rushing home because of fears they would be stuck in Europe, were screened by federal customs and homeland security agents for coronavirus symptoms before they were allowed to leave the airport.

Long lines also formed Saturday in Boston, Dallas and others of the 13 airports that are accepting return flights from Europe.

"People were forced into conditions that are against CDC guidance and are totally unacceptable," Lightfoot said.

Conditions were better Sunday, but lines could again grow as the day progresses and more flights arrive. Not every U.S. airport accepting European arrivals experienced overcrowding. Airports serving Miami, Seattle, Los Angeles and Newark, New Jersey, reported short lines at customs Saturday and Sunday.

For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia. The vast majority of people recover.

Lightfoot singled out Vice President Mike Pence and his coronavirus task force for not talking with local officials before implementing the screening program. State and local officials could have offered "concrete suggestions" for how the program could have been implemented with the least disruption, she said, but the administration acted unilaterally.

"Thousands of travelers were forced to wait in exceedingly long lines, congregating in concourses and putting themselves and their loved ones at greater risk of exposure," Lightfoot said. Passengers Sunday will likely be kept on their planes to manage the flow into the customs area, she said.

But Pritzker predicted Sunday would "be even worse" on NBC's "Meet the Press." He said that the administration should have bolstered staffing at the receiving airports in anticipation of long lines. But instead, he said, passengers "were stuck in a small area, hundreds and hundreds of people, and that's exactly what you don't want in this pandemic."

Texas Gov. Greg Abbot, a Republican and strong supporter of the president, tweeted Sunday that the lines in Dallas were "unacceptable & I'm working hard to get it fixed." He said he had contacted the head of Homeland Security, acting Secretary Chad Wolf.

President Donald Trump defended the administration's actions in a tweet Sunday.

"We are doing very precise Medical Screenings at our airports. Pardon the interruptions and delays, we are moving as quickly as possible, but it is very important that we be vigilant and careful. We must get it right. Safety first!" he wrote.

Acting Customs and Border Patrol Commissioner Mark Morgan said in a written statement Sunday that the agency is making improvements to its procedures, but that it must "balance our efficiencies with ensuring the health and safety of all American citizens through enhanced medical screening."

Katy Rogers spent four hours Saturday at O'Hare in a tightly packed space with students, a basketball team, musicians and older people in wheelchairs.

"Everybody was nervous about it," she said Sunday. "Everyone working there was confused and frustrated, and there were hands were tied, too."

Even though she showed no signs of being sick, she now plans to quarantine herself on the organic produce farm she runs in Noblesville, Indiana.

Elizabeth Pulvermacher, a University of Wisconsin student, arrived Saturday at O'Hare from Madrid, where she had been studying. The customs process made her feel "unsafe," she said.

"The whole idea is getting rid of the spread of coronavirus, but there were hundreds and hundreds of people in very close proximity," Pulvermacher said.

Dr. Robert Murphy, executive director of Institute for Global Health at Northwestern University, said he was "appalled" by what he saw Saturday at nearby O'Hare.

"If they weren't exposed to COVID-19 before, they probably are now. From a public health perspective, this is malpractice," Murphy said in a statement. "The lack of preparation and concern is unfathomable. This is not 'poor planning.' This is 'no planning.'"

Dr. Anthony Fauci, the government's top infectious disease expert, said on "Fox News Sunday" that the airport crowds could spread the disease, but that they are likely to continue. Americans must understand that there is no need to rush back from Europe, he said, but "when people see a travel ban, they immediately want to hunker and get home."

"Hopefully we don't have more of that, but I think we probably unfortunately will," he said.

Travelers from restricted countries in Europe, China and Iran are being advised to self-quarantine for 14 days after reaching their final destination in the U.S.

The worldwide outbreak has sickened more than 156,000 people and left more than 5,800 dead, with thousands of new cases confirmed each day. The death toll in the United States climbed to 61, while infections neared 3,000.