PIEDRAS NEGRAS, Mexico -- Gunmen stormed a party in northern Mexico on Sunday and massacred 17 people, authorities said.
The assailants arrived at the gathering in the city of Torreon in several cars and opened fire without saying a word, the Coahuila state Attorney General's Office said in statement. At least 18 people were wounded.
Several of the victims were young and some were women, but their identities and ages had not yet been determined.
Television footage showed the patio of the house streaked with bloodstains and white plastic chairs overturned beneath a party tent decorated with pictures of snowmen. Police found more than 120 bullet casings at the scene, most of them from .223-caliber weapons.
Investigators had no suspects or information on a possible motive.
Coahuila is among several northern states that has seen a spike in drug-related violence that authorities attribute to a fight between the Gulf cartel and its former enforcers, known as the Zetas.
In May, gunmen killed eight people at a bar in Torreon. Later that month, a television station and the offices of a local newspaper came under fire. A pregnant woman was wounded in the attack on the offices of Noticias de El Sol de la Laguna.
Across northern Mexico, there have been increasing reports of mass shootings at parties, bars and rehab clinics.
In the worst such massacre this year, gunmen raided a drug-rehab center in the northern city of Chihuahua and killed 19 people last month. In January, gunmen barged into a private party in the border city of Ciudad Juarez and killed 15, many of them high school or university students. Relatives say the January attack was a case of mistaken identity, while state officials claim someone at the party was targeted, although they have not said who it was.
The killings in Torreon came three days after the first successful car bombing by drug cartels, an attack that introduced a new threat to Mexico's raging drug war.
The FBI has sent a small team to the crime scene to offer technical assistance to the Mexican investigators, FBI spokeswoman Andrea Simmons said. She did not immediately offer more details.
Mexican investigators have not said what type of explosive was used.
Drug-gang members detonated the bomb after luring federal police and paramedics to an intersection in Ciudad Juarez by shooting a bound man dressed in police uniform and calling in a false report of a wounded officer. Three people were killed, including a federal officer and a private doctor who had rushed to the scene to help.
Officials say 24,800 people have been killed in drug-gang violence since President Felipe Calderon declared war on the cartels in December 2006, deploying soand federal police to fight traffickers in their strongholds.
On Saturday, four municipal police officers patrolling in a truck were ambushed and killed in the Pacific coast resort city of Acapulco, state police said. A threatening message was scrawled on the truck's windshield.
The government attributes much of the rise in violence to infighting among drug gangs, whose leadership has been splintered after the arrest of kingpins.
Federal police said in a statement Sunday that they have arrested 1,626 people suspected of belonging to the command structures of Mexico's drug gangs since Calderon launched his offensive. They said 622 of the detainees belong to the Gulf cartel and 304 to the Sinaloa cartel.
On Sunday, a judge formally charged an alleged leader of the Beltran Leyva cartel, Jose Gerardo Alvarez, with organized crime. Alvarez, who had a $2 million U.S. bounty on his head, was captured in April after soldiers battled his men in a wealthy neighborhood on the outskirts of Mexico City
Three people were killed in the shootout.
The federal government has steadily wiped out the leadership of the once-powerful Beltran Leyva cartel. In December, cartel boss Arturo Beltran Leyva was killed in a gunbattle with marines in the central city of Cuernavaca. Two of his brothers are behind bars.
A fourth brother, Hector Beltran Leyva, remains at large and is believed to be battling for control of the cartel against Edgar Valdez Villareal, a U.S.-born suspect known as "La Barbie."
Mexican authorities say Alvarez partnered with Valdez in his quest for control of the gang.