Mexican soldiers have seized a record 15 tonnes of pure methamphetamine, worth around $4bn (£2.5bn), from a farm in the western state of Jalisco.

The massive haul, which represented half the total weight of worldwide drug haul seizures in 2009, was found stuffed into barrels at a laboratory on a farm in the township of Tlajomulco de Zuniga, just outside Mexico's second-largest city, Guadalajara.

The find is roughly equivalent to the entire economy of the Isle of Man.

The Mexican army said it had received several anonymous tip-offs about the stash.

No one was at the ranch at the time of the raid and no arrests were made, though soldiers confiscated all production equipment.

"It's an historic seizure: more than 15 tonnes of methamphetamine, five kilos of crystal, and around seven tonnes of precursor chemicals," said Gen Gilberto Hernandez Andreu.

It is not known who was behind the drugs but police said the Sinaloa and Los Zetas drug cartels have been active in the area.

The UN Office on Drugs and Crime recently reported that Mexican cartels were increasingly producing synthetic drugs - produced entirely in chemical labs - instead of cocaine.

The seizure was so big it was expected to put an enormous dent in the US market.