Tourists hoping to visit the Skellig Michael monastic site may have to delay their trip after another serious rockfall on the island.
The famous landmark off Kerry was scheduled to reopen to visitors on Saturday for the new 2016 season.
However, that plan is likely to be put on hold after a large boulder broke free from a slope this afternoon, landing directly on the path normally used by walkers.
The Office of Public Works (OPW), which has staff and safety contractors on site assessing the scale of the problem, said the route will remain blocked until the obstruction can be removed.
"The likely impact on this event is unknown at this stage until the matter has been assessed in detail. However, given the obvious implications for visitor safety, it is clear that it may have significant consequences in terms of the planned opening date this coming weekend," it said.
The OPW added that the incident has given rise to "considerable concern", given the large size of the rock and the fact that it came down in a different location from another rockfall earlier this year.
"Both are deeply worrying symptoms that the upper slopes above the roadway remain highly unstable and unsafe," it said.
The state agency said safety staff will attempt to scale the slope above the rockfall location and assess whether other material is likely to break away. Once the area is declared safe, staff will then move in to deal with the boulder on the roadway.
The landmark has recently gained global attention after appearing in the latest Star Wars film.