Palmeiras were frustrated at home by Gremio, who played the last 10 minutes with 10 men after defender Rever went off injured following a clash of heads and their three substitutes already on the pitch. Rever was reported to be out of danger.
Playmaker Cleiton Xavier put Palmeiras ahead after half an hour with a header from Wendel's cross but Gremio equalised within three minutes with a low shot by Argentine striker Maxi Lopez.
"Sometimes it's easier to play away when your opponents go out to attack, than at home," Palmeiras captain and former Brazil keeper Marcos said.
Palmeiras are on 35 points from 17 matches, three points ahead of Goias and four in front of Atletico Mineiro, who have played 16.
Goias beat Flamengo 3-2, their sixth win in a row, with a goal in the last minute by striker Iarley.
Midfielders Amaral and Leo Lima put Goias two up in the opening 24 minutes but former Inter Milan striker Adriano and Serbian Dejan Petkovic pulled them level in the second half.
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Cruzeiro, flying high earlier in the season as they made their way to the Libertadores Cup final, have slumped since losing to Argentina's Estudiantes in the South American title decider last month.
They lost 2-0 at home to Atletico Paranaense and for the second match in a row had two players sent off, bringing their total to 11 red cards in 16 matches in the championship.
Paranaense's Bruno Costa was sent off after 18 minutes, before Cruzeiro midfielder Bernardo was dismissed at the end of the first half and striker Kleber followed in the 70th minute.
Title holders Sao Paulo continued in their rich vein of form, beating Botafogo 3-1 at home for their fourth victory on the trot after falling behind to a goal by playmaker Lucio Flavio.
Jorge Wagner and Washington scored in the last seven minutes of the first half to turn the match Sao Paulo's way and Dagoberto added the third, with his fourth goal in three games.
Promoted Avai won for the fifth time in six matches, 1-0 at home to the also promoted Santo Andre, to continue their surprising run out of the lower reaches into sixth place.
Fluminense ended a run of 11 matches without victory with a 5-1 rout of Sport Recife at the Maracana to leap over their victims out of bottom place.
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