The Italian coastguard has rescued 539 migrants from a fishing boat drifting off the island of Lampedusa.
The rescue on Saturday delivered one of the largest numbers of migrants, which included women and children, to the Italian island in a single day.
Some of the migrants – who had been travelling from Libya across the Mediterranean Sea – displayed signs of violence, the coastguards said.
Italian prosecutors have opened an inquiry into what may have happened.
Alida Serrachieri, a doctor with the humanitarian organisation, Médecins Sans Frontières, also known as Doctors Without Borders, said the migrants appeared to have been physically assaulted by others while in Libya waiting for a boat to take them to Europe.
Investigators suspect the migrants may have been falsely imprisoned in Libya.
Two coastguard vessels and a customs boat from Italy’s financial crimes police, the Guardia di Finanza, helped transport the migrants to Lampedusa.
In May, more than 1,000 migrants landed on the Italian island in the space of a few hours.
The island has a migrant camp that was originally designed to hold fewer than 300 people. There are now more than five times as many, with many more held outside on dusty roads.
Most arrive from countries that do not qualify for asylum.