Huracan snatched the lead in the standings by one point from Velez, who were held 1-1 at Lanus, the other team who began the day with a chance of lifting the title but have dropped out of the picture.
Arsenal were a man short for more than an hour after midfielder Cristian Pellerano was sent off for a second booking and striker Mario Bolatti headed Huracan in front shortly before halftime.
Two goals in the final nine minutes sealed the win. Patricio Toranzo shot into the roof of the net from Javier Pastore's low left cross and less than two minutes later Matias Defederico, who recently won his first Argentina cap, raced between two defenders to steer home the third.
Velez, looking for their sixth league title and first since 2005, have the credentials to spoil Huracan's ambitions with the best defence and only one defeat in 18 matches.
At Boca's Bombonera (Chocolate Box) stadium, Gimnasia took a surpise lead after only three minutes with a headed goal by Uruguayan forward Diego Alonso.
Boca equalised with a penalty by veteran striker Martin Palermo close to halftime but Gimnasia snatched victory with defender Ariel Aguero's header in the 54th minute.
Sixth-placed River's 1-0 loss at Godoy Cruz to a ninth-minute goal by Ivan Borghello helped the home side stay clear of the relegation positions.
