Former Iron striker Billy Sharp had the ball in the net for Sheffield United, but his goal was ruled out for offside.
Almost immediately after, the Owls' doubled their advantage with 14 minutes remaining. Leon Clarke crossed the ball for Marcus Tudgay, who volleyed past Paddy Kenny in the United goal.
Elsewhere in the Championship, West Bromwich Albion remain top of the league after a thrilling 3-3 draw at home to Cardiff.
Two goals from Paul Parry gave the Bluebirds a 2-0 advantage at half time. However the Baggies fought back with a goal from Roman Bednar to narrow the margin.
Joe Ledley then fired in a third for Cardiff, before a strike from Martin Albrechtsen and an own-goal from Roger Johnson helped the home side grab a point.
Bristol City failed to close the gap at the top after they went down 2-0 away at Crystal Palace.
Clinton Morrison opened the scoring after just six minutes with a low drive, and the win was sealed five minutes from time when Mark Hudson headed in a Ben Watson free-kick.
Meanwhile at the foot of the table, Colchester's game with Hull City was postponed, whilst Scunthorpe were beaten at home by Wolverhampton Wanderers.
With eight minutes gone on the clock, Dave Edwards fired the visitors ahead with a low strike, and the win was complete just after the break when £1.5 million signing Sylvan Ebanks-Blake broke through the Iron's defence and slotted past 'keeper Joe Murphy.
Fellow strugglers Preston were beaten away at Stoke City. The home side took the lead after 16 minutes when Leon Cort met a Rory Delap cross from the left.
Richard Cresswell doubled the Potters' advantage with a goal just before the half-hour mark.
Preston pulled a goal back with 68 minutes gone when Chris Brown headed in Lewis Neal's cross. But the win was secured four minutes later when Leon Cort headed in Liam Lawrence's cross for his second goal of the match.
Meanwhile QPR grabbed a much needed win to ease their relegation fears at home to Barnsley.
Patrick Agyemang put the home side ahead after five minutes, and Rowan Vine doubled the lead in first-half stoppage time.
Burnley were victorious away at Coventry, the Clarets coming out top in a 2-1 scoreline.
Finally, there were draws for Ipswich away at Blackpool, Plymouth at home to Southampton and Leicester as they faced Norwich.