While some immigrants had been transferred to other centers, 700 people who entered Italy by boat Sunday and Monday remained at Lampedusa -- a facility designed to hold 190 people, the Italian news agency ANSA reported.
"A plan of action is required," United National Refugee Agency spokeswoman Laura Boldrini said. "The Lampedusa center isn't big enough for these repeated emergencies."
Italy's largest and most militant trade union demanded that the immigrant holding center be shuttered.
While overcrowding complaints have been longstanding, an article last October in newspaper L'Espresso claimed frequent detainee beatings and thefts. It was written by a reporter who posed as a Kurdish migrant.
Some members of Italy's new center-left government have called for overturning tough immigration laws passed by the previous regime, ANSA reported.
Lampedusa is Italy's No. 1 immigrant entry point given its proximity to Africa.