NEWBURYPORT — Mayor Sean Reardon said federal immigration agents on Monday detained an employee at a nail salon here in an enforcement action that left workers and customers shaken.US Immigration and Customs Enforcement agents entered Fantasy Nails on Low Street and detained a male employee before leaving the area, Reardon said in a statement Tuesday.“We have also received deeply concerning eyewitness accounts that agents entered the business with guns drawn,” Reardon said. “This was an incredibly frightening and traumatic experience for the employees and customers inside the business, as well as those who witnessed what occurred.”On Wednesday, the Department of Homeland Security, which oversees ICE, identified the employee as Jun Qiu, a Chinese national who runs the salon, according to business records. DHS disputed Reardon’s characterization of the operation. “Mayor Sean R. Reardon’s claims are categorically false and just another attempt to smear the hard work our ICE agents do every single day,” an agency spokesperson said in a statement. The statement did not specify which claims DHS was disputing or provide details about the arrest. DHS said Qiu entered the United States illegally on Jan. 4, 2019, at an unknown location, and would remain in ICE custody pending removal proceedings. The agency said he “will receive due process.”Police in Newburyport had arrested Qiu at the salon on Friday, court records show. A former employee told police that Qiu had threatened in text messages to kill her and provided the exchanges to local law enforcement, according to police records. Qiu was arraigned Friday in Newburyport District Court on charges of criminal harassment and three counts of threatening to commit a crime. He required a Mandarin interpreter. He pleaded not guilty and a judge released him on personal recognizance with conditions that he abide by a harassment prevention order and have no contact with the former employee, court records show.In its statement, DHS described Qiu’s charges as “three counts of extortion — threats to injure person, and harassing communication.” But court records list the charges as criminal harassment and three counts of threat to commit a crime.Reardon said Tuesday that local officials received no advance notice that ICE would be conducting enforcement in the city. Local police did not take part in the operation, he said.“The City of Newburyport does not condone the manner in which this operation was carried out,” Reardon said. “Federal immigration enforcement should never come at the expense of the safety and sense of security of an entire workplace or surrounding community.”On Tuesday morning, the salon was closed and the lights inside were off. Several local residents who tried to open the door were surprised to find the business was closed.Qiu is scheduled to return to court for a pretrial hearing Sept. 8. Online ICE locator records show that he is being held in federal custody at the Wyatt Detention Facility in in Central Falls, R.I.DHS said that having work authorization or a pending immigration application does not by itself confer legal status in the United States. The agency did not say whether Qiu had either. Reardon said Newburyport officials are working to gather more information about the arrest. He ended his statement with a message to the city’s immigrant community. “If you are an immigrant living, working, raising a family, or running a business in Newburyport, please know that you are a valued member of this community,” Reardon said. “We care about you, and you are part of what makes Newburyport the welcoming and vibrant city that it is.”Giulia McDonnell Nieto del Rio can be reached at giulia.mcdnr@globe.com. Follow her @giuliamcdnr. Nick Stoico can be reached at nick.stoico@globe.com.