Gunmen in Mexico lit a crowded casino ablaze on Thursday, killing at least 53 people in an attack Mexican president Felipe Calderon called an "aberrant act of terror." The brutal assault occurred at the Casino Royale in Monterrey, Mexico's third-largest city. "For more than a year, the city has been the setting for a brutal turf war between rival drug-trafficking gangs that at times have held gunfights on downtown streets in broad daylight," reports The Los Angeles Times. Officials tell the Wall Street Journal that the attack appeared to be linked to drug cartel infighting and that the death toll was expected to rise higher. As many as 80 patrons were in the casino during the fire. "Six hooded gunmen came in, shouting obscenities and firing their guns," said a witness told the Journal. "They drenched the place with gasoline. People were running as the place went up in flames. Those who stayed behind burned to death." The newspaper notes that the violence that is plaguing Monterrey has made the city unrecognizable from years earlier. "Until recently, Monterrey was one of the safest cities in Latin America. But since last year, the city has become a battleground for two of Mexico's most powerful drug-trafficking organizations, the Zetas and the Gulf Cartel, who are fighting for control of lucrative local drug markets and drug routes to the U.S." The attack comes as the U.S. widens its role in helping Mexico fend off its powerful cartels. The AP has raw video from the fire's aftermath below: