One hundred passengers have been reported to Gardaí after arriving at Dublin Airport without a negative COVID test.
The new rules requiring everyone entering Ireland from abroad to present a negative test came into force on Sunday.
The Oireachtas Transport Committee has heard that 95 people who were stopped at the airport had no test to show officials.
Meanwhile, five people were carrying false tests.
The majority of those reported were travelling from Britain on-board Irish airlines.
The Deputy Secretary General at the Department of Justice Oonagh Buckley said the majority were Irish citizens.
She said compliance is generally high – with around 80,000 passengers arriving in to the airport between Sunday and late Tuesday evening.
“In that mix, we checked more than 10% of passengers at all times but in fact, on many flights, we checked 100% of passengers,” she said.
“We referred in those three days only 100 people to An Garda Síochána.”
Failing to provide a negative test can lead to €4,000 fine or one month’s imprisonment – with sanctions increasing for repeat offences.
Passengers without tests are also required to immediately self-isolate and take a test within 36 hours.
Ms Buckley said the Border Management Unit (BMU), which conducts immigration duties, had significantly increased COVID test spot-checks in recent days.
She said the main checks on tests are supposed to be carried out at the point of departure, in line with EU policy.