Israel has delayed an expected release of hundreds of Palestinian prisoners and detainees in exchange for returned Israeli hostages “until further notice,” the Palestinian Prisoners Society said early Sunday.

In what was set to be the largest swap under January’s ceasefire agreement, six hostages were freed, but the release of some 600 Palestinian prisoners was delayed. It comes after Shiri Bibas’s body was returned by Hamas.

Hamas freed two hostages and was set to release four more from Gaza on Saturday in exchange for hundreds of Palestinian prisoners and detainees, after Israel confirmed that a body handed over hours earlier was that of hostage Shiri Bibas.