At least 79 people have been declared dead and hundreds more are missing in what Greece is calling one of the biggest ever migrant tragedies in its waters.

The boat was first spotted in distress off the coast of Pylos, Greece on Tuesday morning. The boat then capsized, causing the Greek coast guard to mount a large-scale search and rescue operation on Wednesday. The court guard alleged that the boat refused several offers of assistance from both its own ships and merchant vessels. They stated that people on board insisted they wanted to continue to Italy, the destination of the migrant boat.

However, Alarm Phone, a network of activists who run a hotline for migrant boats in distress, argued that they had been in contact with people they believe who were on the same vessel and desperate for help. It added that people may have been scared to encounter Greek authorities due to its systematic use of “pushback” measures.

Vincent Cochetel, the UN High Commissioner for Refugees’ special envoy for the Western and the Central Mediterranean tweeted that “the notion of distress cannot be discussed.” Cochetel argued that “this boat was unseaworthy…no matter what some people on board may have have said.” Aerial photos show the boat packed hours before it sank.

As of the time of this report, it is unclear how many passengers are missing. The UN’s International Organization for Migration (IOM) estimates that the vessel may have been carrying as many as 750 people, based on interviews with survivors. So far, survivors that have been found have been brought to the port of Kalamata, where many have been hospitalized with hypothermia or fever.

There has been a recent surge in fatalities for refugee with 2022 marking the deadliest year, according to a report by the IOM. Greece is one of the main routes into the EU for refugees and migrants from the Middle East, Asia and Africa. The UN has registered more than 20,000 deaths and disappearances in the central Mediterranean since 2014, making it the most dangerous migrant crossing in the word. In a statement, IOM Director for the Department of Emergencies, Federico Soda, described the current approach in the Mediterranean as “unworkable,” calling for “collective efforts” to support the human rights of refugees.

The IOM, UNCHR and UN Refugee Agency have all welcomed an investigation into the circumstances which led to the tragedy.