London (AFP) - An investigation was launched Wednesday after a remote-controlled helicopter, suspected to be carrying drugs, crash-landed in an exercise yard at one of Dublin's largest prisons.

The drone plummeted into an exercise yard within Wheatfield Prison in west Dublin at around 10.00 GMT Tuesday.

A package containing suspected drugs was attached by a rope to the four-blade device but it got caught on wires designed to prevent airborne escapes by prisoners.

It's believed up to 20 inmates rushed to the device and managed to gather some of the contraband.

Prison guards noticed the commotion in the yard and intervened.

"We were alerted to an incident at Wheatfield prison yesterday morning," the Garda (police) press office told AFP.

"We were handed a device and an investigation is underway."

The Irish Prison Service also said an internal inquiry was underway and that some prisoners are facing disciplinary procedures.

The drone was highly-sophisticated with a camera that allowed the operators to remotely see where it was travelling.

It's understood a digital memory card onboard the device will be central to the investigation as it mapped the route it took before crashing.

Both the Prison Service and the Garda declined to comment further.