Varanasi, May 16: A probe into the collapse of an under-construction flyover here in Uttar Pradesh that killed 15 people began on Wednesday, officials said.A high-level investigation team constituted by Chief Minister Yogi Adityanath to study the late Tuesday disaster in which half-a-dozen persons were also injured arrived here on Wednesday. The three-member team of Agriculture Production Commissioner Raj Pratap Singh visited the site and collected details of the project from district officials and the team working on the flyover near the Cantt railway station. The team is to submit a report within 48 hours. It also oversaw relief operations.An official told IANS that most vehicles trapped beneath tonnes of concrete and iron have been removed. Deputy Chief Minister Keshav Prasad Maurya and another minister Neelkanth Tiwari rushed to the site. Adityanath also flew to Varanasi past midnight.Four officials have been suspended by Maurya, who is also the PWD minister.Meanwhile, after close monitoring by the Prime Minister's Office (PMO), a FIR has been lodged under sections 304, 308 and 427 of the Indian penal Code (IPC) against the UP Bridge Corp and the executing agency constructing the flyover. Modi represents Varanasi in the Lok Sabha.Work on the flyover, which would connect Chaukaghat and Lahartara, began on October 1, 2015 when Akhilesh Yadav was the Chief Minister. The construction has been marred by controversies, an official said. In 2017, soon after the Bharatiya Janata Party (BJP) took power in Uttar Pradesh, work on the project was expedited and the Bridge Corp was given a deadline of March 2019 to complete the work.The officials had, however, thrown up their hands in despair with the new deadline owing to heavy traffic movement on the segment and sought October 2019 as the new deadline for completion of the 1,710-metre-long flyover. The cost of the project is Rs 77.41 crore and 63 pillars are to be built. However, till now, only 45 pillars have been put up. Bahujan Samaj Party supremo Mayawati on Wednesday demanded stern action against the guilty.