The Justice Minister is asking anyone with information about a missing person's case to come forward.
It comes as the country marks National Missing Person's day.
There are 876 long-term missing people on the island of Ireland.
The sister of Trevor Deely says his disappearance has caused trauma for 21 years, and is renewing her families appeals for information.
Michelle Deely's appeal comes as part of National Missing Persons Day.
Trevor was 21 when he vanished after attending a Christmas party in Dublin on December 8th, 2000.
At today's virtual remembrance ceremony, Justice Minister Helen McEntee pleaded with anyone who has information about any case to come forward.
There is also an appeal from Gardai - Commissioner Drew Harris is encouraging any family members of missing persons to submit DNA samples.
He says this could play a vital part in solving cases.
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