The Save the Children aid group reported another migrant tragedy on Tuesday, with survivors saying dozens of their fellow passengers fell out of their rubber boat and likely drowned in the Mediterranean as a rescue vessel neared.

The exact toll wasn't known, the group's Giovanna di Benedetto said from Catania, Sicily. But she said that survivors, in their first interviews with aid officials once they reached shore, reported that people fell into the sea and couldn't swim.

The incident is believed to have occurred on Sunday in the sea between Libya and Sicily when a commercial vessel approached to rescue the migrants. The vessel arrived in Catania on Tuesday, and the survivors disembarked.