The seven aged between 22 and 24-years-old from around the Pas-de-Calais region including Calais were arrested at the scene near Dunkirk.
According to reports they beat up four Iraqi-kurds who were waiting by the road to try to board trucks bound for the UK.
The gang were found to be carrying iron bars and were picked up by police not long after the violent attack.
The migrants are believed to have come from the nearby Grande-Synthe migrant camp where hundreds of Kurds are living in squalid conditions.
The arrests come after numerous reports of migrants in the Calais region being attacked in recent months.
“I do not know if these people are those who carried out previous attacks,” said prosecutor Eric Fouard.
According to Medecins du Monde, a charity working in the area to improve conditions for migrants, the number of attacks has risen since the beginning of the year.
“Tens of people have been beaten up with iron bars in Calais, leaving them with multiple fractures,” she said.
“These kind of attacks occurred last summer and in September but now they are more regular,” she said.
The migrant crisis in northern France has created tensions between migrants and police as well as locals.
An anti-Islam rally planned for Calais last Saturday was cancelled as police feared it could lead to trouble.
There have been regular clashes between riot police and migrants in recent months.