Guano!

Drug agents in Peru say they have seized three tons of cocaine mixed into a shipment of guano bound for Spain.

A four-month investigation led to the seizure at a warehouse in the capital of Lima, anti-drug police Col. Cesar Cortijo said Monday.

Cortijo said the drugs belonged to a trafficking ring that smuggled cocaine out of the country mixed with other products. Four Peruvians and a Colombian were arrested.

Police delayed announcing the Dec. 4 raid because it was initially impossible to calculate how much cocaine was mixed with the guano, the nitrogen- and phosphate-rich droppings of birds and bats.

Peru is the world's largest producer of coca and cocaine after Colombia, and it is also a major source of guano, harvested from excrement-stained islands off its southern coast. Most is used as fertilizer in Peru's fields, but some is shipped overseas, where it is a favorite among organic gardeners.