Emergency services were called at around 2.15am and police closed the road in both directions between the Thrussington junction and the A6006 Dalby turn off, including all junctions between.
The Melton Times is awaiting comment from Leicestershire Police on the incident - a force spokesman said investigations were ongoing and further details will be released later.
The southbound lane, from the Seagrave turn, was reopened to traffic around 8am but the northbound lane, from the A6006 Wymeswold junction to the A6 Wanlip turn, remains closed at this time.
Area traffic controllers say there is huge congestion at Syston, as a result of the closure, and that HGVs are advised to divert via the A6 to Loughborough.
More to follow.