MEXICO CITY – Federal police found 18 tons of explosives that had been stolen hours earlier in northern Mexico, the federal Public Safety Secretariat said.

The industrial-use explosives were stolen by a group of unknown assailants from a tractor-trailer on a highway near the border between the states of Nuevo Leon and Coahuila, prompting federal police and army soldiers to launch an operation to relocate the material.

The shipment was later recovered on a highway leading to the industrial city of Monterrey, Nuevo Leon’s capital.

Security forces across that region of the country, which borders the United States, had been put on alert after Friday’s theft.

The truck carrying the cargo had departed from the northwestern state of Durango on Thursday afternoon but never arrived at its destination in the eastern state of Tamaulipas, Coahuila state Attorney General Jesus Torres said.

Mexico has been beset by drug-related violence in recent years, with roughly 17,000 killed in gangland mayhem nationwide as heavily armed cartels fight over supply routes.

Drug-related homicides have continued to rise despite President Felipe Calderon’s deployment of 50,000 soldiers and 20,000 federal police to combat the narcotics mobs.

But other organized criminal activity from kidnapping to human smuggling to highway robbery of merchandise also poses a serious problem.

According to figures from the National Autotransport Cargo Chamber, or Canacar, robberies of cargo vehicles rose 40 percent in 2009 relative to the previous year.