Lucknow, Jul 28 (IANS): The National Investigative Agency (NIA) on Friday formally started a probe into the discovery of an explosive substance in the Uttar Pradesh assembly near the seat of the Leader of Opposition.

The team headed by Inspector General J.P. Singh scanned through the rooms of the state assembly around noon and checked the Central Hall and other places, an official said.

They also checked the room of the Vidhan Sabha Principal Secretary.

Highly explosive material PETN -- a white powdery substance -- was recovered from near the seat of Ram Govind Chaudhary.

Chief Minister Yogi Adityanath had related the incident with terrorism and termed it a serious breach of security. He had requested the matter be probed by the NIA.

The Ministry of Home Affairs on Thursday formally approved the request after which a formal probe by the NIA has been initiated.

The Anti Terrorism Squad of the Uttar Pradesh Police, which was probing the matter with some assistance from the NIA, has been asked to brief the team about the details collected so far.

The NIA team also spoke to some assembly staff and is likely to question some legislators who were earlier questioned by the ATS.

Samajwadi Party legislator and former minister Manoj Pandey and Anil Dohre along with a dozen other persons were earlier questioned by the ATS.

The team has already met Principal Secretary (Home) Arvind Kumar and taken down details about the incident. CCTV footage has also been handed over to the NIA officials.