An Iranian cancer researcher who was detained at Boston's Logan International Airport has been sent back to his home country along with his wife and children.

Mohsen Dehnavi, 32, and his family were put on a return flight to Iran shortly after 9pm Tuesday, after the US Customs and Border Patrol denied him entry at Boston's Logan Airport.

US Customs and Border Patrol spokeswoman Stephanie Malin said the Dehnavis family's detention was for 'reasons unrelated' to President Donald Trump's executive order on travelers from six predominantly Muslim countries.

Malin said the stop was based on information discovered during the agency's review. She didn't elaborate.

Dehnavi was arriving in the US to start work at a prominent Boston hospital.

Trita Parsi, an Iranian-American activist, said Mohsen Dehnavi had sent him this picture of his entry visa after being denied entry to the US and sent back to Iran on Tuesday

Boston Children's Hospital said in a statement earlier Tuesday that 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 the reasons for the detention were unclear.

'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 US,' hospital spokesman Rob Graham said in the statement.

'The hospital is committed to doing its utmost to support Dr. Dehnavi and his family.'

But CBP spokeswoman 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.

Dehnavi was detained Monday at Boston's Logan Airport, seen in a file photo, for 'reasons unrelated' to Trump's travel ban on individuals from six countries, including Iran

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 DC-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.

Boston Children's Hospital is seen in a file photo. Dehnavi had a J-1 visa to work at the hospital, but border officials said he was detained due to information discovered during review

'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.

During the 2016 presidential campaign, Trump had called for a 'complete and total shutdown' of Muslims entering the United States, a move he called necessary to protect national security in the wake of attacks at home and abroad by Islamist extremists.