Substitute Ronald scored a last-minute winner to keep Swansea top of the Championship after their match at Millwall was held up due to alleged racist chanting aimed at the visitors’ Eom Ji-Sung.
Referee Edward Duckworth halted the match in the 65th minute and walked to the dug-outs at the Den to speak with Lions boss Alex Neil, Swans counterpart Vitor Matos and fourth official Ruebyn Ricardo. Eom had been warming up as a substitute at the time.
A security guard was also on the scene, with referee Duckworth seeming to point to an area in the stands behind the Swansea dug-out.
When play eventually resumed after almost seven minutes it was announced in the stadium that there had been a report of racist chanting, adding that police were working to identify any offenders using CCTV.
The game itself had a dramatic finale with table-topping Swansea scoring a last-gasp winner.
Swansea arrived in south London with the best defensive record in the division and they showed why as Millwall dominated the first half.
The Lions should have gone ahead after 10 minutes when Mark Sykes crossed low to Kyrell Lisbie, who looked set for a tap-in until Filip Lissah made a last-ditch tackle.
Moments later Jenson Metcalfe thought he was through on goal but this time on-loan Sunderland defender Jenson Seelt, making his first Swans start, got back to make a vital challenge.
A neat flick from Lyndon Dykes then teed up Sykes six yards out but Swans goalkeeper Lawrence Vigouroux made a fine save.
Vigouroux then came for and missed a Metcalfe corner, but Jordi Osei-Tutu's header was deflected onto the roof of the net.
Swansea managed just one shot on target in a one-sided first half, a tame effort from Zan Vipotnik which was easily dealt with by Lions keeper Filip Marschall.
The visitors got a sniff of a chance early in the second half after Derek Mazou-Sacko was booked for a foul on Moussa Yeo, but Josh Tymon sent the free-kick over the crossbar.
Lions captain Jake Cooper then had to hack Joseph Opoku's shot off the line before Yeo fired narrowly over as the leaders began to exert more authority.
Vipotnik slipped in Yeo but Cooper was on hand to make a timely interception, before Mazou-Sacko made another goal-line clearance to deny Ross Stewart.
After the delay in play, Millwall searched for a winner and Vigouroux made a point-blank save to deny Dykes and Tristan Crama headed the resulting corner over.
But Swansea nicked it at the death when Opoku crossed, Millwall hesitated and Brazilian winger Ronald crashed home the winner.
Millwall's Alex Neil:
"I'm disappointed. I didn't think we deserved to lose.
"First half I thought we were the team looking threatening and they were under the cosh. But we didn't take our chances."
Swansea's Vitor Matos:
"I think it was a lucky substitution by the manager.
"It was a really intense game, a good game, Millwall started really well. But I think we did it really well to deal with that, we stayed organised. That allowed us to grow into the game."
