At least 60 economic migrants have been injured after they set fire to a detention centre on the Italian island of Lampedusa.Tensions boiled over when more than a hundred Tunisian illegal immigrants were told they would be sent back by plane. There has been unrest at the Lampedusa camp since the Italian government turned it from a transit centre into a permanent site from where migrants are expelled back to North Africa. The United Nations has criticised overcrowding there. Lampedusa, which is south of the island of Sicily, has been a staging post for migrants seeking to come to Europe by boat from Libya. The Italian government has introduced tough new immigration laws which means the migrants are now kept at Lampedusa until being granted asylum or are expelled. Last month detainees broke out of the facility and marched into a local town to protest about conditions. Most migrants reaching Italy by sea last year applied for asylum and more than half are normally given the right to stay in Europe. Calm has now been restored after police used tear gas to end the latest unrest A local mayor on the island said detainees setting fire to the camp had been a gesture of despair.