BRUSSELS (AP) — The European Union's official watchdog said Wednesday it has opened a probe in the role of the bloc's Frontex border agency in the shipwreck off Greece last month that is feared to have killed hundreds of people in the Mediterranean Sea.

Migrant crossings in unseaworthy boats organzied by human traffickers from Northern Africa have spiked this year, with massive losses of life.

Now, EU ombudsman Emily O'Reilly wants her investigation to make clear to the public “who is accountable for these deaths” as Frontex has unclear jurisdiction and limits to its authority over member states like Greece when it comes to addressing the needs of those in distress on the high seas.

Key questions raised by the tragedy include to what extent the EU’s Frontex agency could have been more involved in the rescue, what exactly did it communicate to Greek authorities and what level of responsibility, if any, the agency has for the shipwreck.

“A tragedy of this magnitude requires all those involved to reflect on their responsibilities and to be clear to the public who is accountable for these deaths," Ombudsman O'Reilly said.

As many as 750 people may have been on board the migrant ship that sank in the Mediterranean on June 14, and just over 100 people survived the shipwreck. So far, 82 bodies have been recovered and hundreds of people are missing.

Greece has been widely criticized for not trying to save the migrants before the sinking in international waters. Officials in Athens say the passengers refused any help and insisted on proceeding to Italy, adding that it would have been too dangerous to try and evacuate hundreds of unwilling people off an overcrowded ship.

The ombudsman's probe comes on top of Greek authorities looking into the responsibilities of their own coastguard in the tragedy.

"It has been reported that in this instance Frontex alerted the Greek authorities to the ship’s presence and offered assistance but it is not clear what else it could or should have done,” said O’Reilly.

Any new analysis coming out of the investigation could help those adrift in the Mediterranean in the future, she said.

___

Associated Press writer Renata Brito reported from Barcelona.