Hopes faded of finding survivors of the latest Mediterranean boat tragedy, in which an estimated 200 migrants drowned, on Thursday as rescue ships were called to the aid of more migrant boats in the same area.

Vessels from the Italian and Irish navies and humanitarian agency Medecins sans Frontiers (MSF) saved more than 370 people from a capsized boat thought to be carrying up to 600 on Wednesday, the Italian coast guard said.

They recovered 25 bodies but found no more survivors after scouring the waters overnight. Italian vessels continued to search the area on Thursday, a coastguard spokesman said.

Initial reports put about 700 passengers on the overcrowded fishing boat but interviews with survivors – mostly Syrians fleeing their country’s civil war – reduced that estimate and the figure could still change.

Seas were very calm on Thursday, perfect conditions to attempt the sea crossing, said a Reuters photographer aboard the privately funded Phoenix, a vessel run by MSF and the Migrant Offshore Aid Station.

The Phoenix was responding to a distress call for a boat carrying about 500 people, he said. The coastguard picked up 381 on Thursday morning, while an Italy navy ship took 101 from a large rubber boat, and the MSF vessel Argos rescued 87, according to their Twitter accounts.

The Italian navy said it was handing out life preservers to “numerous” migrants on yet another boat.

Wednesday’s tragedy occurred when the boat flipped over as an Irish rescue vessel approached, probably because desperate passengers surged to one side as they spotted the ship, LE Niamh, on its way to help them.