Mexican authorities have arrested a state police officer in connection with last week's casino arson fire in Monterrey that killed 52 people.
The Associated Press reports a surveillance video shows the officer in a vehicle outside the upscale Casino Royale. Few other details were immediately released.
Authorities arrested five other suspects, believed to be members of the Zetas drug cartel, on Monday.
Investigators have not given a motive for the killings, but they are exploring whether drugs or an extortion plot are behind the attack.
Last week, gunmen carrying a flammable liquid burst into the casino and began setting fires as workers and patrons ran for cover.
The attack was one of the worst on civilians in Mexico in recent years.
More than 40,000 people have been killed in drug related violence in Mexico since President Felip Calderon launched a national crack down on drug cartels in 2006.