Eleven Irish people were arrested and detained by British police yesterday during a protest outside the Sellafield nuclear plant in Cumbria.
Those detained included five women and six men who were formally cautioned last evening before being set free. They are due home today.
A spokesman for the police said 10 were arrested for highway obstruction and one for causing criminal damage to a road sign.
He said they had blocked the main road outside the nuclear plant in a "very disruptive" demonstration. It prevented many people, including train drivers and teachers, getting to work and a number of train services had to be cancelled, he said.
He added that some of group had chained themselves together on the highway.
The demonstration started at 6 a.m. and involved up to 120 Irish people who had travelled by bus from Limerick and Dublin for the protest, which was organised by a number of environmental groups, including Globalise Resistance and Gluaiseacht.
Insp Paul Coulson said a formal caution meant those arrested now had a "bad mark" against them which would be recorded on computer but they would not have a criminal record. All had been co-operative, he added.
A spokesman for Globalise Resistance, Mr Joe Carolan, said last night the protests at Sellafield would continue.
"There are going to be hundreds of people involved in civil disobedience until the plant is closed down," he said.
"We are just so sickened by the inaction of mainstream politicians on this issue. That is why young Irish people are now willing to highlight this case and take non-violent direct action. To allow Sellafield to continue to damage the health of people on the eastern seaboard is criminal and we don't feel we are breaking any laws," he added.
Meanwhile, a report of a review of energy options in the UK, presented to the British government yesterday, said action should be taken to retain nuclear-powered electricity plants. The report from the Performance and Innovation Unit (PIU) was welcomed by British Nuclear Fuels.