The Health Department doesn't know how many travellers are coming into Northern Ireland via Dublin and is "struggling" to get data, MLAs have been told.
The Health Committee heard it was "not really possible" to give a number for visitors via the Republic of Ireland because the locator forms were paper - but that it should be resolved in the coming weeks.
Today a leaked letter from the Health Minister to his Irish counterpart, seen by PA, revealed his concerns about the "inability" to share information about passengers going between the jurisdictions, and "serious impediments" to monitoring quarantine.
In it Robin Swann said the "logical" step would be to make all international arrivals give contact information, available to agencies on both sides of the border.
But Alliance MLA Paula Bradshaw, who sits on the Health Committee, said it was "pointless" to talk about quarantine without effective contact tracing.
She added: "The Health Minister is not wrong in what he says about passenger location forms, but should have been getting on with implementing a comprehensive tracing and testing system at all ports of entry and encouraging the authorities in the Republic to do likewise."
Speaking to MLA's on Thursday, Health Department official Elaine Colgan said they were working with Border Force to "get a handle" on how many people were giving an NI address for their place of isolation.
Asked by the DUP 's Pam Cameron how many "external" visitors were arriving in NI ports, Ms Colgan said: "Data is something we are struggling with in terms of the number of people coming in and we are putting mechanisms in place.
"In terms of people coming into the South and then coming up to the North because the locator form is still a paper form, it’s still not really possible to desegregate how many there are but hopefully that will be resolved over the next few weeks."
She added: "We are also working with Border Force to try to get a handle on the number of passenger locator forms being filled in for any arrival where they've put a NI address as their self isolation point. Work is well underway to get that data."
