The American Civil Liberties Union said Monday it is looking into an incident in which a Border Patrol agent detained and questioned a woman and her friend — both U.S. citizens — when he overheard them speaking Spanish at a gas station in Montana.

The incident occurred early Wednesday morning at a convenience store in Havre, Mont., a town in the northern part of the state, near the border with Canada.

Ana Suda said she and her friend, Mimi Hernandez, were making a midnight run to the store to pick up eggs and milk. Both are Mexican American and speak fluent Spanish, and they had exchanged some words in Spanish while waiting in line to pay when a uniformed Border Patrol agent interrupted them, Suda said.

“We were just talking, and then I was going to pay,” Suda told The Washington Post. “I looked up [and saw the agent], and then after that, he just requested my ID. I looked at him like, ‘Are you serious?’ He’s like, ‘Yeah, very serious.’ ”

Suda said she felt uncomfortable and began recording the encounter with her cellphone after they had moved into the parking lot. In the video Suda recorded, she asks the agent why he is detaining them, and he says it is specifically because he heard them speaking Spanish.

“Ma’am, the reason I asked you for your ID is because I came in here, and I saw that you guys are speaking Spanish, which is very unheard of up here,” the agent can be heard saying in the video.

Suda asks whether they are being racially profiled; the agent says no.

“It has nothing to do with that,” the agent tells her. “It’s the fact that it has to do with you guys speaking Spanish in the store, in a state where it’s predominantly English-speaking.”

Suda, 37, was born in El Paso and raised across the border in Ciudad Juárez, Mexico, but has spent much of her adult life moving around the United States with her husband and young daughter. Hernandez is originally from central California, Suda said.

Despite explaining this to the agent and showing him their IDs, Suda said, he kept them in the parking lot for 35 to 40 minutes. Though no one raised their voices in the video, Suda said she and Hernandez were left shaken and upset by the encounter, which ended around 1 a.m.

“I was so embarrassed … being outside in the gas station, and everybody’s looking at you like you’re doing something wrong. I don’t think speaking Spanish is something criminal, you know?” Suda said. “My friend, she started crying. She didn’t stop crying in the truck. And I told her, we are not doing anything wrong.”

When she got home, Suda posted on Facebook about what had taken place at the gas station. She said her shock began to give way to sadness in the following days, after some local news outlets reported the incident, and her 7-year-old daughter asked whether the video meant they should no longer speak Spanish in public.

“She speaks Spanish, and she speaks English,” Suda said. “When she saw the video, she was like, ‘Mom, we can’t speak Spanish anymore?’ I said ‘No. You be proud. You are smart. You speak two languages.’ This is more for her.”

A representative from U.S. Customs and Border Protection told The Post the agency is reviewing the incident to ensure all appropriate policies were followed. Border Patrol agents are trained to decide to question individuals based on a variety of factors, the agency added.

“U.S. Customs and Border Protection agents and officers are committed to treating everyone with professionalism, dignity and respect while enforcing the laws of the United States,” the agency said. “Although most Border Patrol work is conducted in the immediate border area, agents have broad law enforcement authorities and are not limited to a specific geography within the United States. They have the authority to question individuals, make arrests, and take and consider evidence.”

Havre is a rural town with a population of about 10,000, about 35 miles south of the U.S.-Canada border. Border Patrol agents have broad authority to operate within 100 miles of any U.S. border, though they cannot initiate stops without reasonable suspicion of an immigration violation or crime.

Suda said she is used to seeing Border Patrol agents in Havre because it’s so close to Canada, especially at gas stations, but had never been stopped before.

“It’s a nice town. I don’t think it’s a confrontational [population] here,” Suda said. “But now I feel like if I speak Spanish, somebody is going to say something to me. It’s different after something like this because you start thinking and thinking.”

Suda said Sunday she planned to contact the ACLU to seek legal guidance.

“I just don’t want this to happen anymore,” Suda said. “I want people to know they have the right to speak whatever language they want. I think that’s the most important part, to help somebody else.”

The ACLU on Monday said speaking Spanish is not a valid reason for a Border Patrol agent to question or detain someone.

“There’s citizens whose first language isn’t English or who are limited in English and that doesn’t mean they are committing an immigration offense,” said Astrid Dominguez, director of the ACLU’s Border Rights Center. “The constitution prohibits racially profiling. You need to have reasonable suspicion [of an offense before detaining someone] and speaking Spanish isn’t one of them.”

Dominguez said this was the first instance she had heard of that involved someone being stopped and questioned for speaking Spanish, and that the civil-rights organization would be speaking with Suda to talk about next steps.

“The broader picture … goes back to accountability at the agency,” Dominguez said. “Is this the way they’re targeting people? It is an issue, and it needs to be addressed.”

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