More than 300 kg of synthetic drugs valued at $7.8 million have been seized by Mexican army troops in Tijuana city, near the border with San Diego, the defence secretariat said.
The quantity of drugs was sufficient to produce nearly 942,000 doses, it said.
The drugs were found packed in 276 plastic bags in a house near the US border, it said, adding that a vehicle was also seized during the operation.
Tijuana, in Baja California state, has been plagued by drug-related violence for many years as rival drug gangs fight for control of smuggling routes to the US.
The government has seized over 43 tonnes of chemicals used to produce synthetic drugs since December 2006, when President Felipe Calderon took over.