A bus driver in Maine told passengers they needed to be U.S. citizens to ride on a bus while an immigration official questioned passengers’ citizenship.

The incident happened in the city of Bangor over Memorial Day weekend, the ACLU of New Hampshire said in a video statement.

The footage shows passengers being confronted by a U.S. Customs and Border Protection agent.

“Are you folks U.S. citizens?” the CBP agent asks.

“I’m not answering that question, sir,” a man says in the video.

Later on, a bus driver for Concord Coach Lines can be heard telling passengers they need to be U.S. citizens to ride.

“Do you have to be a U.S. citizen to take this bus?” a passenger asks.

“Yes,” the bus driver responds.

“You have to be a U.S. citizen to take this bus?” the man asks again.

“I doubt that,” a woman off to the side can be heard saying.

As the ACLU points out, no one is obligated to answer questions about their citizenship just to ride a bus.

Concord Coach Lines vice president Ben Blunt told New Hampshire Public Radio that the employee misspoke.

“I think if we are remiss in anything here, it’s not doing a good enough job talking about this issue with our staff,” Blunt told the station.

“We don’t want to ask our employees ― our drivers, our ticket agents ― to be interfering with a federal officer who is lawfully doing his job,” Blunt added.

In a statement to HuffPost, CBP defended the actions of its agent.

“Enforcement actions away from the border are within the jurisdiction of the U.S. Border Patrol and performed in direct support of immediate border enforcement efforts and as a means of preventing smuggling and criminal organizations from exploiting existing transportation hubs to travel to the interior of the United States,” the statement said. “These operations at transportation hubs serve as a vital component of the U.S. Border Patrol’s national security efforts.”

The incident has come to light just days after reporters were finally allowed to view a facility in Texas holding immigrant children whom the U.S. government has separated from their parents.

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This is at least the second time that Border Patrol agents have harassed people attempting to ride a bus. In January, Border Patrol agents in Florida asked Greyhound passengers for the IDs and took a woman into custody.

Greyhound officials said they are following the law by letting Border Patrol agents question their passengers. But the ACLU said Greyhound has the right and responsibility to demand a warrant for Border Patrol officers to board its buses.

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This article originally appeared on HuffPost.