"The Tunisian Red Crescent confirmed on Thursday that there were still bodies in the water and the recovery operation was ongoing," said the agency in a statement.
"It also said that 150 people, mostly sub-Saharan Africans, had died and their bodies taken to Sfax Hospital."
The vessel was packed with refugees, many fleeing the conflict in neighbouring Libya. It was heading for the Italian island of Lampedusa when it hit a sandbank and capsized as people struggled to leave the boat to jump into rescue vessels, the TAP news agency reported.
Some 600 people were rescued, but, as of Thursday, up to 270 were missing and rescue workers said there was little hope of finding more survivors.