Williams spoke with the referee after hearing the alleged abuse when he was preparing to take a corner in the first half, and play was held momentarily as supporters were warned.
Turkish teenager Arda Guler's strike helped Real Madrid close in on the Spanish title with a 1-0 win at Real Sociedad on Friday, moving 14 points clear at the top of La Liga.
Laporta demanded the Spanish football federation and the refereeing committee send Barcelona all footage of the incident and audio recordings of the officials' conversations.
The coach was furious after Lamine Yamal had a shot which Barcelona said crossed the line not given as a goal after officials could not prove that it had using VAR.
The Catalan side have 68 points, seven ahead of Atletico Madrid, who visit Alaves on Sunday, and 10 clear of fifth-placed Athletic Bilbao, who drew 1-1 at home to Granada on Friday.
Barca moved to 70 points, eight behind leaders Real Madrid, whom they will face in the "El Clasico" at the Santiago Bernabeu next weekend.
Antoine Griezmann scored twice as Diego Simeone's men moved to within four points of their opponents and pulled five clear of fifth-placed Athletic Bilbao in the race for Champions League qualification.
"(Saul) entered the game well and scored a great goal," Simeone told Movistar.
A second-half header by winger Raphinha earned second-placed Barcelona a 1-0 win over Las Palmas in LaLiga on Saturday after the visitors were reduced to 10 men in the first half.
Lewandowski set up goals for Joao Felix and Fermin Lopez either side of striking himself to pull Barcelona second, eight points behind leaders Real Madrid.
La Liga leaders Real Madrid regained their seven-point cushion at the top on Sunday as they benefited from two own goals in a comfortable 4-0 home win over struggling Celta Vigo.
"Getting the three points at home is the most important thing to be at the top," said defender Yan Couto.
The Spanish Football Federation (RFEF) suspended the 20-year-old for showing contempt towards referee Jesus Gil Manzano after receiving a red card in Real's 2-2 league draw with Valencia on Saturday.
After Real Madrid drew in Valencia the night before, surprising title challengers Girona had a chance to reverse their recent slump and regain some ground.
It takes Real to 65 points ahead of Barcelona, in second after they beat Getafe 4-0 on Saturday, and nine in front of third-placed Girona before they host Rayo Vallecano on Monday.
Barca moved to second in the standings on 57 points, five behind leaders Real Madrid and one ahead of third-placed Girona, both of whom have a game in hand.
Valencia's league match against Granada that had been scheduled to take place on Saturday has been postponed following a deadly fire in the eastern coastal city, LaLiga said on Friday.
Spain's La Liga chief Javier Tebas believes it is almost certain that superstar striker Kylian Mbappe will be playing for Real Madrid next season, he told French daily L'Equipe in an interview published on Friday.
After leaders Real Madrid were held to a draw by Rayo Vallecano on Sunday, the Catalan minnows, second, hoped to cut the six-point gap but lost in a gripping clash at San Mames.