A Delhi police team came to Calcutta on Monday to interrogate people who could be connected to Lalit Jha, named the "mastermind" behind the Parliament security breach.

The team interrogated a person suspected to be associated with Jha at the Girish Park police station. The police did not divulge the identity of the person.

The Delhi officers also visited Jha's Rabindra Sarani address but found it locked. They tried to contact the owner of the room, where Jha and his family spent several years, to try and get hold of the key to the lock, but it could not be opened till late on Monday evening.

A resident of Rabindra Sarani said the owner of the building where Jha had rented a room lives in Delhi. "The owner lives in Delhi; he had given the keys to a local caretaker. A team from the Delhi police came today but found the room locked. They tried to contact the owner and went away," the resident said.

The one-room apartment has been locked since the Jha family left the locality. People in the neighbourhood said there was “some problem” after which the family left and Jha locked the room before leaving.

It is not clear if the lock on the room that the Delhi police found was the one put by Jha or a different one hung by the landowner.

The team stationed itself at Girish Park police station, in whose area the Jhas had rented a house after they left Rabindra Sarani.

An officer with Calcutta police said the team from Delhi had interrogated several people from the neighbourhood and was trying to ascertain the identity and details of the students whom Jha used to teach.

Jha, known as “masterji” in the neighbourhood, used to give private tuitions in Burrabazar.

Several residents of Rabindra Sarani said they used to see children and young adults enter the one-room apartment where he lived.

Another team from the central intelligence bureau visited the house of college student Nilaksha Aich on Monday in Halishahar, North 24-Parganas, 48km from the heart of Calcutta.

Sources in the police said the central team interrogated Nilaksha and his father and sought details of the NGOs he was associated with. “They also asked about the funds and finances of the NGO and asked for bank statements of the NGO’s accounts,” said an officer with Bengal police.

Shefali Sardar, the landlady at the Baguiati house where the Jhas have lived for much of the past three years, said no cops had visited their home in connection with the probe on Monday.

“We will share whatever information we have. But except the first day, no one has come here,” she said.

She said the room where Jha lived and had locked before he left for Delhi on December 10 had been left untouched.

Jha had left the Baguiati apartment with a backpack, saying he was going to Delhi and would return in “three-four days”.