Irish officials will again attempt to evacuate Irish citizens from Libya after a Government plane left Tripoli on Wednesday night without any passengers.
The Casa aircraft arrived in the troubled north African state at around 4.50pm but Libyan security prevented the officials from airlifting the Irish citizens wishing to leave.
The aircraft remained on the ground for four hours but later returned to Malta. The Department of Foreign Affairs said efforts would resume on Thursday.
Irish diplomats are also working with EU officials to have Irish citizens accommodated on other European flights trying to get out of Tripoli.
It is understood there are around 70 Irish citizens in Libya, where ruler Muammar Gaddafi has ruthlessly cracked down on protests over his 42-year autocratic regime. Some 54 are in the capital Tripoli.
The Casa aircraft joined a LearJet which flew into Malta on Tuesday night for a possible evacuation. The Casa aircraft, routinely used for fisheries patrols, can carry 21 people.
Outgoing Taoiseach Brian Cowen approved the immediate deployment of the two Air Corps planes Foreign Affairs officials have been liaising with European Union counterparts to establish options to assist citizens and help them leave the country safely.
The evacuation is being co-ordinated by Pat Hennessy, the Irish ambassador in Rome who is accredited to Libya.
There are at least six Irish workers in Libya's second city Benghazi with Dublin-based firm Mercury Engineering. Four women who hold Irish passports are long-term residents in the city and married to Libyan men.
The department spokesman added: "Efforts are continuing with EU partners to look at options with regard to the Irish citizens remaining in the eastern part of Libya." More than 200 people have been killed in the past two nights of clashes on the streets of Libya, with Mr Gaddafi vowing to fight "to my last drop of blood".