The National Investigative Agency (NIA) on Saturday began a probe into the discovery of high-grade PETN explosive inside the Uttar Pradesh assembly, an official said.
Officials said that the NIA team arrived here late on Friday and was immediately briefed about the case.
The NIA officials, other than visiting the spot where the Pentaerythritol Tetranitrate explosive was discovered on Thursday evening, were also likely to grill the security staff and agencies of the state police responsible for security of the Vidhan Sabha.
The state security personnel would be quizzed on as to why no action was taken to spruce up security despite a tip-off from the Intelligence Bureau (IB) in May about a possible terror plot to attack the state assembly when in session.
The NIA team would also question the House marshals and other security staff along with janitors and others who has access to the exclusive area, near the seat of Leader of Opposition.
A senior security official informed IANS that many a times the lawmakers refuse to cooperate with the security and throw a tantrum on being frisked.