Copenhagen police swooped on illegals during last night and this morning, arresting 17 E. Europeans and one American, according to a police news release.
Those arrested have not been named.
The 17 E. Europeans were either Romanians or Bulgarians, many of whom had illegally entered premises such as a disused storage warehouse and a burnt-out house.
Seven of those arrested were found in a disused post office building where a Romanian group was discovered in July and deported on charges of illegal camping and unauthorised overnight stays.
The July deportations have resulted in a debate as several legal experts have said that the move contravenes EU rules stipulating that EU nationals can only de deported from another EU country in the event of serious crime.
The European Roma Rights Centre (ERRC) in Budapest has said it is to sue Denmark claiming the unjust expulsion of 23 Roma who were deported from Denmark last month for squatting in the disused post office and camping on Amager Fælled,
The ERRC, which enjoys EU funding, was set up to monitor human rights conditions for European Roma and initiate legal proceedings in the case of violations.
It is not immediately clear where or why the American national was taken into custody.
Edited by Julian Isherwood