Five suspects were arrested in connection with the attack last week on a casino in Monterrey, the capital of the northern Mexican state of Nuevo Leon, that left 52 people dead, officials said Monday.

The five men confessed to the attack and told investigators that it was linked to an extortion attempt against the owners, Nuevo Leon Gov. Rodrigo Medina told Televisa.

Some of the suspects appear on videos from security cameras at Monterrey's Casino Royale, Medina said.

Investigators have not yet determined which criminal organization the men belong to, the governor said.

The investigation to find out who was involved in the torching on Thursday afternoon of the Casino Royale is at a "crucial stage," Medina said.

Gunmen riding in two vehicles arrived at the two-story Casino Royale around 3:50 p.m. Thursday and torched the business, eyewitnesses said.

A total of 52 gamblers and employees trapped inside the casino died, with most of the deaths due to smoke inhalation, officials said.

"I can tell you, without providing too many details to avoid hindering what we are doing at this time, that we already have five people under arrest who participated in different things having to do with what happened at the Casino Royale, all of whom have confessed," Medina said.

Authorities are conducting an "important (operation) to determine the whereabouts of two other people who have emerged from the questioning," the governor said.

Investigators have reviewed video from the casino's security cameras with the suspects, who provided details about "the participation of other people" in the attack, as well as identifying some individuals who served as lookouts, Medina said.

The suspects have also given investigators information about an "agreement on payments and extortion" with the casino, the governor said.

"Some of them (the suspects) said from the outset that there was pressure or extortion that may have been brought to bear directly against the owners or management of the casino to get some amount of money," Medina said.

The casino torched last week is owned by Grupo Royale, which has gambling establishments in the cities of Monterrey, Mazatlan, Los Cabos and Escobedo.

Opened three-and-a-half years ago, the casino's first floor has space for about 250 people and features slot machines, roulette wheels and other games, while the second floor has poker tables.

One of the industry's problems is that casinos are operating in Nuevo Leon that "just have a federal permit and were not approved by the municipalities," Medina said.

"There is disorder due to the proliferation" of the establishments, "which are sometimes the scene of illegal activities" or "are subjected to extortion," the governor said.

About 4,000 people took part in a protest march on Sunday to demand an end to the drug-related violence in Monterrey, Mexico's most important industrial city.

The protesters marched to the Governor's Palace and called for Medina's resignation.

The federal government is deploying 3,000 Federal Police officers and army troops in Monterrey to bolster security in the wake of the attack on the casino.

Monterrey and its suburbs have been battered by a wave of drug-related violence since March 2010, when three rival cartels reportedly went to war with Los Zetas, considered the country's most violent criminal organization.

Los Zetas has been battling an alliance of the Gulf, Sinaloa and La Familia drug cartels, known as the Nueva Federacion, for control of the Monterrey metropolitan area and smuggling routes into the United States.

A total of 267 murders were registered in Monterrey in 2009, with the figure rising to 828 in 2010 and more than 1,100 so far this year, according to official figures.