BOSTON -- An Iranian cancer researcher arriving in the U.S. to start work at a prominent Boston hospital has been detained at Logan International Airport.

Boston Children's Hospital said in a statement Tuesday that Dr. Mohsen Dehnavi was prevented from entering the country with his wife and three young children despite holding a J-1 visa for visiting scholars. They arrived at the airport Monday.

The hospital said in a statement that the family could be deported, but it hoped they would be allowed to enter the U.S.

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"[Dehnavi] and his family are being detained at Logan are supposed to be sent back to Iran later today," the hospital said in a statement. "Boston Children's hopes that this situation will be quickly resolved and Dr. Dehnavi and his family will be released and allowed to enter the U.S. The Hospital is committed to doing its utmost to support Dr. Dehnavi and his family."

U.S. Customs and Border Patrol spokeswoman Stephanie Malin said the Dehnavis family's detention was for "reasons unrelated" to President Trump's executive order on travelers from six predominantly Muslim countries. She said the stop was based on information discovered during the agency's review. She didn't elaborate.

But Malin noted that visa applicants "bear the burden of proof" to meet all requirements and can be denied entry for a range of reasons, including health-related issues, criminality or security concerns.

The Supreme Court recently ruled the Trump administration could largely enforce its temporary ban on travelers from Iran, Libya, Somalia, Sudan, Syria and Yemen. But the court said the ban can't block people with a "credible claim of a bona fide relationship with a person or entity in the United States."

Some advocacy groups, including the American Civil Liberties Union and the National Iranian American Council, suggested the detention might be a violation of the Supreme Court order.

"The family is very worried," said Shayan Modarres, a lawyer for the D.C.-based council, which has been in contact with the family. "If it is a minor paperwork issue, then something needs to be told to the family so they can resolve it."

At the very least, the incident shows how the administration's political priorities are leading to "overzealous enforcement" of immigration laws, said Gregory Romanovsky, chair of the New England chapter of the American Immigration Lawyer's Association.

"Exercising discretion is not what they're comfortable doing anymore, especially if they're dealing with someone from one of the six banned countries," he said of local customs officials. "The travel ban and the whole anti-immigrant mood coming from the very top of this administration certainly affects their ability."

Boston Mayor Marty Walsh, a Democrat, told reporters he was waiting to hear more about the Dehnavis' circumstances, but also suggested the case was an example of concerns with the travel ban.

"Many people, doctors and nurses and people who are students working in the world-class institutions that we have are going to be boxed out or left out of the country," he said.