New Delhi: Delhi police on Thursday claimed to have solved the CBSE paper leak case, saying the mastermind was a teacher who had been taken into custody earlier this month.

Police said Rakesh Kumar, who taught at DAV school in Una town of Himachal Pradesh, was the brain behind the leak of the Class X math and Class XII economics papers.

The crime branch had last week arrested Rakesh and two employees of the school - Amit Sharma and Ashok Kumar - in connection with the leak of the economics paper.

Alok Kumar, joint commissioner (crime branch), said three more persons, including the manager and the cashier of a bank in Una where the question papers were kept in lockers, had been arrested too.

"Both the manager and the cashier were the custodians of the sealed question papers and they were supposed to be present when the bank locker was opened by the exam centre's superintendent (Rakesh). But they violated the guidelines of the CBSE by not being present there and gave access to Rakesh alone. They have been charged with criminal negligence," the officer said.

"Rakesh Kumar had been teaching at the DAV school as a PGT economics teacher for eight years. He was also involved with the leak of the math paper before the scheduled date of the exam on March 28," the police officer said. The economics paper, he added, was leaked on March 23, three days before the examination date, and shared on nearly 40 WhatsApp groups.

Rakesh was the centre superintendent of Jawahar Navodaya Public School in Una, where the CBSE exams were being held. Amit Sharma worked at DAV school as a clerk and Ashok Kumar as a peon.

"After taking photos of the math paper on his mobile, he (Rakesh) called one of his students (not being named as he is a minor) to his house and got it handwritten and took photos of the same on his cellphone. Later, he sent it to a female relative in Firozpur (Punjab) through WhatsApp," joint commissioner Kumar said.