After 40 minutes, shots were heard in the stadium. The 20,000 spectators were immediately crouched to protect themselves and the players ran to the locker room. It turned out that the shots came from outside the stadium, to the point of safety.
A gunman opened fire on security guards at the entrance of the stadium, injuring a policeman.
The shooting erupted when security guards asked to stop a vehicle because of the weapons it contained. The driver refused to comply.
Police did not say who the gunmen were, but Torreon has recently been the scene of fighting between the powerful Sinaloa and Zetas drug cartels.
Torreon is located about 621 miles north of Mexico City in the border state of Coahuila.