At least 36 migrants drowned when their boat sank off the Libyan coast earlier this week, officials said, following the recovery of more bodies on Sunday.
The navy said it rescued 52 people when the boat sank on Tuesday, but survivors say there were 130 people on board.
On Saturday Libya's interior minister urged the European Union (EU) to do more to help stem the tide of migrants.
Libya is the preferred crossing point for many African migrants trying to enter the EU.
Libyan navy spokesman Ayoub Kassem told the BBC that the boat capsized about 4km (2.5 miles) out to sea near the Libyan coastal town of Garabouli.
The bottom of the boat had collapsed, causing it to capsize, he said. At least 54 people remain missing, he added.
On Sunday 24 more bodies were recovered from the sea near Garabouli, bringing the death toll to 36.