The pair came together in a first-half incident when Swans captain Williams tried to wrestle the ball from Mahrez, who scored a hat-trick in the Foxes' 3-0 win.
The pair were later involved in an altercation outside the Swansea dressing room, before the Algeria international was ushered out of the stadium by a Leicester official.
Williams brushed past reporters a few moments later asking where the Leicester bus was and went outside the stadium to the visitors' waiting coach.
But Press Association Sport understands that Williams did not get on the bus before returning to the stadium.
Asked about the incident at his post-match press conference, Swansea manager Garry Monk said: "I wouldn't know anything about it."
A Leicester spokesman said Mahrez did not try to enter the Swansea dressing room, but declined to make any further comment on the incident.
Leicester's victory took them back to the top of the Premier League after Manchester City had lost 2-0 to Stoke earlier in the day.
Swansea remain four points above the relegation zone after winning only one of their last 11 games, with the defeat piling further pressure on under-fire Monk.
Source : PA
Source: PA