Arsenal appeared to be on its way to a victory which would have put it one point off the top when Milton Caraglio opened the scoring in the 18th minute, but Facundo Pereyra levelled just after the hour mark.
The match finished in heated fashion after a dispute about the state of the ball and what the home side saw as time-wasting.
The referee was forced to halt the match as police came on the pitch to attempt to break things up, and in the end Damian Perez and Nicolas Aguirre for Arsenal were sent off, as well as Gimnasia's Ariel Garcia, Franco Mussis and Ricardo Diaz.
Newell's, meanwhile, surrendered a lead to draw 1-1 with Godoy Cruz, who levelled on the hour through Jose Luis Fernandez after Horacio Orzan opened the scoring in the seventh minute.
Boca Juniors moved level on 24 points with Arsenal as it beat Colon Santa Fe 2-0 with two quickfire first-half goals.
Emanuel Gigliotti opened the scoring in the 20th minute, with Juan Manuel Martinez adding a second moments later.
In the day's other game, Carlos Luna netted on the stroke of half-time to give Rosario Central a 1-0 win at Belgrano Cordoba.