Nine Egyptian men who were aboard a migrant boat that sank off the coast of Greece last year, killing hundreds of people, are to face trial next month, accused of people smuggling, Greek judicial sources said on Friday.

The circumstances of the sinking of the Adriana in June remain a source of dispute between the Greek authorities and groups supporting the rights of survivors and migrants — meaning the trial could be the first opportunity to officially hear the accounts of some of those present at the time.

Survivors have accused the Greek coastguard of capsizing the boat. The authorities, which monitored Adriana for hours, say it overturned when a coastguard vessel was about 70 metres away. The coastguard service has denied any wrongdoing.

It remains unclear what happened in the time between the coastguard being alerted to the presence of the vessel and when it capsized.

In a report in December, EU border agency Frontex — which had spotted the boat from the air before the coastguard — said that Greek authorities failed to reply to its follow-up calls and its offers for assistance. It said it could not conclude what caused the Adriana to capsize.

The overcrowded fishing trawler was carrying hundreds of migrants from Pakistan, Syria and Egypt when it sank off the southern town of Pylos, in international waters, on its way from Libya to Italy. Some 104 men survived and only 82 bodies have been recovered.

It was the worst disaster in years and again highlighted the dangers for migrants crossing the Mediterranean Sea to Europe.

The nine Egyptian men, in pre-trial detention since June, have been charged with causing the incident, participating in a criminal organisation, migrant smuggling and other charges, one of the sources told Reuters. They have denied any wrongdoing. The trial is set to begin on May 21 in Kalamata. Rights groups have opposed their detention.

NGO Legal Centre Lesvos demanded that the charges against the nine be dropped and they, “Be immediately released and provided with appropriate psycho-social support as survivors of one of the deadliest shipwrecks in the Mediterranean in recent years.”

Last year, survivors recounted how a doomed attempt by the Greek coastguard to tow the trawler capsized the vessel. Their statements contradict the accounts of the Greek government and the coastguard, which said the boat had refused assistance.

In September, 40 survivors filed a lawsuit against Greek authorities accusing them of failing to intervene to rescue those on board and causing the vessel to capsize.