Celtic are eight points clear at the top of the Ladbrokes Premiership following a spiteful 4-1 win over Motherwell at Parkhead.
After a slow start by the leaders goals from winger Scott Sinclair and striker Odsonne Edouard had them comfortably ahead by the interval.
An otherwise uneventful match turned sour six minutes after the break when Gboly Ariyibi reduced the deficit with a controversial goal, as the home side thought they were initially getting the ball back from a throw-in.
The match continued to the soundtrack of boos from the angry Hoops fans before Edouard curled in a free-kick in the 88th minute to ease the tension, with substitute Oliver Burke adding a fourth.
In ending the Steelmen's six-game winning run in the league, Brendan Rodgers' side made it 14 home wins out of 14 in the league to retain their advantage over Old Firm rivals Rangers, who had closed the gap with a 5-0 win at Hamilton earlier in the day.
However, the ramifications from Motherwell's goal could go on for a while.
The afternoon had started on a positive note.
Celtic fans were delighted to see the return of left-back Kieran Tierney for the first time since December 13, after recovering from a hip injury, and he was handed the captain's armband in the absence of suspended Scott Brown.
Sinclair, Nir Bitton, Edouard and 18-year-old Ewan Henderson were also handed starts, the latter his first for the Hoops, while James Scott replaced the absent Curtis Main in the Motherwell attack.
Celtic, as usual, made the running in the early stages but the visitors stood firm.
In the 21st minute, Edouard was booked for a challenge on Tom Aldred which saw the Well defender led off with a head injury and he was replaced by Carl McHugh.
The defensive change disrupted Motherwell and Celtic's struggle ended in the 31st minute when Ryan Christie's whipped-in cross from the left was met by Sinclair who volleyed in from six yards.
The home side swarmed around the opposition penalty area looking for a second which came six minutes later when Edouard got on the end of a Henderson cross to bullet a header in at the near post.
Motherwell's goal soon after the interval had the Hoops players and fans in uproar.
Celtic had thought they were getting possession back from Liam Grimshaw's throw-in after the ball had been put out for Christie's injury.
However, with Tierney off-guard, Scott raced down the right and when his angled drive was parried by keeper Scott Bain, Ariyibi slid the rebound into the net to spark off a melee.
Players from both sides pushed and shoved amid loud boos which rained down from the stands.
Jack Hendry replaced Christie and the ill-feeling continued and when Conor Sammon came on for Scott, the departing Well player was barracked by the home support.
In the 77th minute Well substitute McHugh was carried from the field on a stretcher after a challenge with Edouard and was replaced by Liam Donnelly.
Celtic, imbued with a sense of injustice, finished strongly. With two minutes remaining Edouard's free-kick from 25 yards – after he had been fouled by Allan Campbell – crashed in off the bar and then Burke, on for Bitton, slammed in a fourth from 12 yards after taking a James Forrest pass.
