Photo of a pigeon. iStock

Police in Argentina shot down a suspicious pigeon that was attempting to deliver a secret haul of drugs to a jail, prison authorities have said. The bird was sniped out of the sky after it was spotted circling the grounds of a penal colony in Santa Rosa.

Officers found that a cloth 'backpack' had been strapped to the pigeon, which contained marijuana, a USB drive, and sedative pills. The pigeon was heading for Unit 4 of the prison located within Argentina's La Pampa Province.

Aware of similar instances of contraband smuggling using carrier pigeons, the region's police observed the bird before eventually capturing it.

"[The contraband] was tied with a piece of cloth in the form of a backpack, inside which there were narcotics, according to the [analysis]", a Federal Penitentiary Service source told Clarín newspaper (via Google Translate).

The drug stash consisted of 44 pills deemed to be Rivotril and Clonazepam, and 7.5g of marijuana. The purpose and content of the USB drive was not disclosed.

The report also notes the sender was likely attempting to avoid detection by timing the pigeon's trip to coincide with a local celebration that saw 15,000 pigeons released into the sky. The huge flock took flight from the town of Toay, which is located around 10km away from Santa Rosa.

Argentine prison officers had been alerted to the possibility of drug-traffickers using pigeons after an investigation in 2013 led to the arrest of three people and the seizure of 15 pigeons. Some reportedly made between 10 to 15 trips per day.

A similar method of drug-delivery to prison inmates was also reported in Costa Rica in 2015. The pigeons were dubbed "narcopaloma" by local media, which roughly translates to "drugs dove".