He said the ‘threat’, an unmarked communication, came from an ‘unnamed immigration officer’. One of the placards Jakob was holding at a protest made a reference to the Holocaust in Germany: ‘1933-1945, we have been there’.

Another sign that he was holding read: ‘Uninformed criminals = criminals’.

In a video doing the rounds on Twitter, Jakob is heard justifying his interest in taking part in the civilian protests, saying he is showing solidarity because “human rights are an issue everywhere”. Jakob’s protest assumes significance because critics have compared the current situation in India to that of Nazi Germany.

Another German student, who did not want to be named, was seen at one of the protest venues holding a placard that read: “If you let this happen to your fellow citizens, your grandkids will be really pissed with you… trust me.”

Jakob’s friends at IIT-M are distressed at the development.

“It is very sad that a friend might get deported for simply showing solidarity,” said his friend on condition of anonymity.

“Freedom of expression is being curtailed in India, which claims to be democratic. He protested only peacefully,” said another friend, who participated in a protest. Many more have tweeted in support of Lindenthal.

ChintaBAR, an IIT-Madras student group, in a Facebook post on Monday extended, “solidarity and gratitude to Jakob, for being part of struggles to protect the rights of people in this country and his concern for humanity.”

The Ambedkar Periyar Study Circle at IIT-Madras in a Facebook post said, “APSC strongly condemns this action by the government and stands in solidarity with Jakob.”

The management of IIT-Madras did not reply or confirm any of the details when Express contacted them. The director of the institution Bhaskar Ramamurthi did not answer phone calls.