Brazilian Serie A leaders Internacional scored a goal in each half to secure a 2-0 win over Vasco da Gama on Sunday but the home side said they were contesting the result because the Video Assistant Referee (VAR) wasn't working properly.
Vasco said they will seek to annul the result because "the VAR stopped working right at the moment when it was to check the Internacional goal."
Inter's Rodrigo Dourado scored with a header after 10 minutes to give the visitors the lead.
However, TV pictures showed the attacker was in a possibly offside position.
Dourado told reporters at half time the referee had informed him there was a problem with the VAR at the time of the goal.
The referee made no reference to the controversy in his match report but the Brazilian Football Confederation (CBF) later admitted there was a problem with the offside lines and would seek "clarifications" from Hawk-Eye, the company responsible for the VAR machines.
Nevertheless, "the first Internacional goal was checked by the VAR team and there was no clear error by the on-field referee," the CBF said in a statement.
The home side had a chance to level the scores with eight minutes left but Cano sent his penalty kick wide and then the league's joint top goalscorer Thiago Galhardo guaranteed the points for Inter with a stoppage time strike.
Inter, who are chasing their first league title since 1979, are on 69 points, one ahead of second-placed Flamengo with two games to go.
The two sides meet in Rio de Janeiro next weekend.
The result was a huge blow to Vasco, who are aiming to avoid relegation to the Serie B.
The Rio club are fourth-bottom of the table with 37 points from 36 games, a point behind Bahia. The bottom four sides get relegated.
(Reporting by Andrew Downie; editing by Richard Pullin)
