Muzaffarpur police on Monday arrested a 22-year-old for the Staff Selection Commission's multitasking non-technical staff (MTS) examination paper leak after he was detained at his test centre on Sunday.

The question paper of the Allahabad-headquartered SSC exam was available on WhatsApp an hour before the exam began at 10am on Sunday. Muzaffarpur senior superintendent of police (SSP) Vivek Kumar said the arrested youth, Ravi Kumar, had a paper sample on his phone that was identical to the actual question paper.

"A youngster who had the question paper sample on his WhatsApp was arrested after he was detained at the examination centre on Sunday," said SSP Vivek Kumar. "The police later checked the question paper circulated on social media with the original question paper and both were identical. We have gathered leads after interrogating him."

Ravi, a resident of Hilsa in Nalanda district, had been detained from the St Xavier's School exam centre gate in the town's Mithanpura area. It is not clear if the question paper was leaked from Bihar or from outside as the Sunday examination was being conducted by the Allahabad-based SSC to select junior staff for central government departments.

Patna police, based on media reports, have taken cognisance of the paper leak. "Prima facie our job is to find out from where the paper was leaked," said an officer. "The SSC MTS examination held last month was also leaked but that time the leak was not from Bihar."

Chief minister Nitish Kumar said: "The police are probing the case as a FIR has been lodged, but the Centre has to decide as the paper leaked was of a central government exam."

Officers are also probing if the case has a link with Nalanda as people involved in the Bihar Staff Selection Commission (BSSC) leak and those attempting to leak the National Eligibility-cum-Entrance Test (NEET) have connections there. "We are establishing the links of the case with Nalanda, if any," said a senior police officer. "The role of people from Nalanda district in leaking question papers of competitive tests has come to the fore. Sanjeev Kumar, also known as Guru, is involved in the BSSC and NEET cases."

While Sanjeev is from Nagarnausa in Nalanda, his son Shiv Kumar was arrested for the NEET leak attempt.