A new specialised net costing €250,000 has been installed over the main yard at Mountjoy Prison to prevent drugs being thrown over the perimeter wall.

The Irish Prison Service says it has dramatically reduced the supply of illegal drugs into the prison and says further nets will be installed.

Residents on Glengarriff Parade, which backs onto the perimeter wall of the jail have been plagued for years by drug dealers climbing onto the roofs of their homes and throwing drugs packages into the prison.

The new net over the prison yard is translucent, fire resistant, tough enough not to rip when heavy objects are thrown on to it and fine enough to catch even the smallest packages.

Twice a day Prison Officers collect what has been thrown in. Before the net was installed, larger slabs were been thrown over, but now even drugs put into in hollowed out egg shells are not getting through.

The nets have so far been installed in two prison yards - the remaining seven will be covered within two months.

Last year, gardai arrested 75 people in one day for throwing drugs into Mountjoy but Prison Authorities say they have now closed off one of the most effective methods drug dealers had for smuggling drugs into the country's biggest prison.