Hamas drugged hostages so they appeared "calm and happy" when released from captivity in Gaza, an Israeli official said on Tuesday after a one-week truce that saw scores freed collapsed.

Israeli officials say Hamas militants seized about 240 hostages and took them to Gaza in their October 7 attacks on southern Israel, which killed 1,200 people, mostly civilians.

Of these, 105 were released during the Qatar-mediated truce which ended on Friday and halted devastating fighting inside the Hamas-ruled Gaza Strip, where the government media office says more than 16,200 people have been killed, again mostly civilians.

Hagar Mizrahi, head of general medicine at Israel's health ministry, told lawmakers that sedatives such as Rivotril, also known as Clonex, had been given to some of the hostages before their release last month.

"They (Hamas militants) gave them Clonex pills to make them seem calm and happy before they were handed over to the Red Cross," Mizrahi told parliament's health committee.

She did not specify whether the information was based on blood tests or witness accounts, or how many hostages she was referring to.

"They also gave them a little to eat just before their release, so that they left captivity in good form," Mizrahi said.

Of the 105 hostages released, 80 Israelis were freed in exchange for 240 Palestinian prisoners in Israeli jails under the terms of truce agreement.

Five others were released before the truce, including one rescued by Israeli troops.

According to the Israeli authorities, 138 hostages remain in Gaza.