Nuevo Leon state attorney general Alejandro Garza y Garza said that between 20 and 30 gunmen abducted four guests and a receptionist from the 17-story Holiday Inn in Mexico's industrial hub, which has seen a surge in violence recently.
The gunmen had with them a handcuffed man who led them to the fifth floor, Garza y Garza said. The assailants stormed room 517 where an Asian guest was staying, realized he wasn't who they were looking for and left, he said.
The group then searched at least seven more rooms on the fifth floor, apparently looking for specific targets, before going across the street to the Hotel Mision where they abducted a receptionist, the attorney general said.
Those abducted included three male guests who registered at the Holiday Inn as businessmen from Mexico City and a woman registered as from the border city of Reynosa, across from McAllen, Texas.
Garza y Garza said a private security guard who was outside the Holiday Inn has been reported missing but that it remains unclear if he was abducted by the gunmen.
Organized crime was likely behind the attacks, the state attorney general said.
"A lot of what we're going through right now is part of a readjustment among cartels," Garza y Garza told a news conference in Monterrey.
Still, it was not clear exactly what motivated the abductions or who the victims were.
Local media reported that the gunmen hijacked several trucks and used them to barricade two main avenues about 15 blocks from the hotels, presumably to prevent authorities from reaching the area. But Garza y Garza said police were still investigating that.
He said the attackers stole a computer containing the Holiday Inn's hotel registry and the hotel's security videos.
The U.S. Consulate in Monterrey denied media reports that an American woman had been kidnapped from the Holiday Inn, and it repeated warnings to U.S. citizens to be wary of violence in Nuevo Leon state.
Violence by battling drug cartels has become increasingly intrusive in Monterrey, where drug cartels have tried to confound police and soldiers by blockading roads with stolen, sometimes-burning vehicles.
Authorities say the violence is the result of a split between the Gulf cartel and its former ally, the Zetas drug gang.
On March 19, two university students were killed in the crossfire of a shootout between gunmen and soldiers outside the gates of their campus.
Since those shootings, at least three U.S. universities have suspended their exchange studies programs in Monterrey.
In one wealthy suburb on Monterrey, the mayor created a group of private crime fighters, unaffiliated with police and paid with donations by local businessmen - a security force he now says will be disbanded.
Mayor Mauricio Fernandez of San Pedro Garza Garcia said the group was "smeared" by allegations it might itself be involved in illegal activities.
He previously said the group would perform "rough work, I would call it cleansing" and suggested it might operate outside the law.
Elsewhere, police found the bound bodies of two men in the Mexican city of Cuernavaca, alongside a banner that threatened to kill 25 more drug cartel members.
Police said the killings are part of a battle between traffickers Hector Beltran Leyva and U.S.-born Edgar Valdez Villarreal, known as "La Barbie."
Cuernavaca police said the bodies were found early Wednesday outside a bar.
A message left near the cadavers said 25 of Beltran Leyva's henchmen are being held and interrogated in the Pacific coast resort of Acapulco and would be executed soon.
Late Wednesday, a clash between soldiers and gunmen in a Mexico City suburb left two alleged gunmen dead, said Guadalupe Sanchez, a spokeswoman for federal prosecutor in Mexico state.
In the border city of Tijuana, the Mexican army seized about 19 tons of marijuana that was packed and ready to be shipped north of the border, Gen. Alfonso Duarte said Wednesday.
State police reported that three men were found shot to death Tuesday in a taxi in Acapulco. It was unclear whether they were related to the drug dispute.
An estimated 22,700 people have been killed in Mexico's drug war since December 2006, when President Felipe Calderon launched a U.S.-backed military crackdown on drug cartels.