More than 500 migrants crammed themselves into a single boat and had to be rescued on Aug. 28.

The Italian coastguard intercepted the fishing vessel struggling to carry 539 people off the shore of Lampedusa.

Authorities discovered evidence of torture on at least 20 survivors, who came from North Africa, West Africa, and Bangladesh.

The Independent revealed the migrants had endured a long journey from Libya via the Mediterranean Sea.

Doctors Without Borders (MSF) suspects the group, including women and children, suffered fire burns and gunshot wounds while waiting several weeks–or months–for the fishing boat to depart.

“[They] were very worn down, some were dehydrated,” MSF nurse Alida Serrachieri said according to the publication.

The Italian government is investigating the matter, and suspect the migrants could have been wrongfully detained in Libya.

“Militias fight with each other or with government forces,” the UNICEF website said.

Libya has experienced civil war ever since 2014.

“Children in Libya, including refugee and migrant children, continue to suffer grievously amidst the violence and chaos unleashed by the country’s longstanding civil war,” the organization said in a statement.

Although the detention centers in question are state-run they are prone to human smuggling, under the direction of militants.

“Many traffickers arrive in the center overnight, forcing the soldiers to give them groups of migrants to make them work for free,” one Libyan detention center director said according to UNICEF. “They are very dangerous people, armed, and ruthless. They make no distinction between adults and children.”

Two other small boats arrived at Lampedusa on August 28, each carrying 27 and 15 migrants respectively.

Lampedusa, Italy’s southernmost point, has become a prominent entry point for migrants into Europe.