Gunmen Attack Mexico Rehab Center, at Least 10 Die

While police have not identified the motive in the Tijuana slayings, drug gangs have attacked such centers before to target rival gang members.

In Ciudad Juarez, prosecutors' spokesman Arturo Sandoval said three municipal police officers were found shot to death outside their patrol vehicle on Sunday.

And in the southern Pacific coast state of Guerrero on Sunday, state police found the bound, executed bodies of six men on a highway outside the resort city of Acapulco.

The men had been blindfolded, their hands and feet bound, and shot to death with assault rifles, the state Public Safety Department reported.

The killers left three handwritten messages with bodies, a tactic frequently employed by Mexico's drug gangs to threaten their rivals or authorities, but police routinely do not reveal the contents of such messages.

Nationwide, more than 28,000 people have been killed in drug gang violence since December 2006, when Calderon deployed soldiers to battle the cartels in their strongholds in northern Mexico and along the Pacific coast.

While the government says most of the dead were involved in the drug trade, innocent bystanders have also died, like three people killed in the crossfire of a shootout between gunmen, police and soldiers in northern Coahuila state Sunday.

The victims were a 14-year-old boy and two women aged 18 and 47, according to a statement by the state prosecutors' office.

The statement said gunmen traveling in two vehicles opened fire on a convoy of federal police officers and soldiers in the city of Saltillo, Coahuila. The officers and soldiers returned fire.

It was not clear who fired the shots that killed the bystanders, but the state attorney general's office said it was investigating and expressed condolences to the victims' families.

"They are civilians who unfortunately died in the exchange of gunfire," it said, describing a running series of confrontations between police and assailants who allegedly fired shots into the air to clear bystanders from their path at one point.