An investigation has been opened into the actions of a Minneapolis police officer who questioned someone on a train about the status of their immigration.

The incident which took place on the 14 May, came to light after artist Ricardo Levins Morales posted a video of the discussion.

The film shows the officer asking a man for his name, state identification and if he was in the US legally.

Morales told Storyful that the officer had been spot checking customers aboard the train to check if they had paid for a ticket, and the man was unable to produce any proof of payment.

In the video, Morales is heard asking the officer if he's authorised to act as immigration police. "No, not necessarily," the officer responds. The officer is then warned that it is tricky legal territory.

It is unknown what exactly happened to the man afterwards as the next stop was the final stop of the service.

Metro Transit Police Chief John Harrington said: "I immediately called for an Internal Affairs investigation to gather the details about this incident and to report back to me as quickly as possible.

"It is not the practice of the Metro Transit police to inquire about the immigration status of our riders. Our policy states: 'It is the policy of the Metro Transit Police Department that all members make personal and professional commitments to equal enforcement of the law and equal service to the public. Confidence in this commitment will increase the effectiveness of this department in protecting and serving the entire community and recognising the dignity of all persons, regardless of their immigration status.'

"Metro Transit and our parent organisation, the Metropolitan Council, believe strongly in the need for our riders to feel safe in our relationship with our officers. The main priority for our officers is to ensure that our riders and the communities we serve are safe.

"Our officers do this by enforcing our local and state statutes and have not been trained or empowered to act as Federal Immigration authorities."