The armed wing of Hamas said Saturday’s anticipated second batch of hostage releases would be postponed until Israel agreed to allow relief trucks into northern Gaza.

The al-Qassam Brigades of Hamas warned hostage releases would be postponed if Israel did not follow through on the agreed-upon parameters for the release of Palestinian captives.

There was no immediate Israeli response to the statement. Earlier an Israeli military spokesperson had told France’s BFM television station that, barring last minute changes, 13 Israeli hostages were expected to be freed.

He said 39 Palestinian prisoners would be released in return.

Under the truce deal between Israel and Hamas, mediated by Qatar, a total of 50 hostages are to be exchanged for 150 Palestinian prisoners, some of them convicted on weapon charges and violent offences, over four days.

In the first exchange on Friday, 13 Israeli women and children – out of around 240 hostages captured by Hamas fighters on a killing spree in southern Israel on Oct. 7 – were released. Twenty-four jailed Palestinian women and 15 teenagers were released from Israeli jails.

Saturday’s setback came just hours after Egypt, which controls the Rafah border crossing into southern Gaza through which vital aid supplies have resumed, said it had received “positive signals” from all parties over a possible extension of that deal.

Diaa Rashwan, the head of Egypt’s State Information Service (SIS), said in a statement that Cairo was holding extensive talks with all parties to reach an agreement which would mean “the release of more detainees in Gaza and Palestinian prisoners in Israeli jails.”

Israel has said the ceasefire could be extended if Hamas continues to release hostages at a rate of at least 10 per day. A Palestinian source has said up to 100 hostages could go free.

Israel and Hamas have said hostilities would resume as soon as the truce ends, although U.S. President Joe Biden said on Friday there was a real chance of extending the truce.