Hamas released another set of human remains Friday, a day after the terrorist group released what it said was the body of hostage Shiri Bibas — but turned out not to be hers, officials said.

The incident caused outrage from Israeli officials, and the Israel Defense Forces called it “a very serious violation” of a strained ceasefire agreement.

Hamas called it a mistake, and said that Bibas’ remains may have been “mixed” with others when they were hit by an Israeli airstrike.

Hamas leader Mahmoud Mardawi told media outlet Al Arabiya that Bibas’ remains have now been returned.

The International Red Cross also said that it has received a set of human remains and transferred them to Israeli officials. A spokesperson for Israel’s Ministry of Health said it is prepared to do forensic testing.

The body initially believed to be that of Bibas, along with the remains of her two young children, Ariel and Kfir Bibas, and 84-year-old Oded Lifshitz were returned Thursday in a Hamas ceremony in which the militant group placed four black caskets on a stage.

The Israel Defense Forces said hours later that testing determined that the bodies were those of her children but not Shiri Bibas.

The remains also did not match any other hostage held by Hamas, the IDF said. “It is an anonymous body without identification,” it said.

Israeli Prime Minister Benjamin Netanyahu accused Hamas of “an unimaginably cynical act,” and said that Hamas failed to return Bibas and “instead placed the body of a Gazan woman in the coffin.”

Bibas and her two children were abducted from their kibbutz, Nir Oz, in the Oct. 7, 2023, Hamas attack against Israel. Ariel was 4 years old and Kfir was just shy of 9 months old when they were taken. They were the two youngest hostages.

Shiri Bibas’ husband, Yarden Bibas, was taken separately and released by Hamas on Feb. 1 as part of the ceasefire agreement.

Israel’s military said Ariel and Kfir were “brutally murdered in captivity” in November 2023.

IDF spokesman Rear m. Daniel Hagari said Friday that the children were not shot, but that “they killed them with their bare hands.”

“Afterwards, they committed horrific acts to cover up these atrocities,” Hagari said.

Hamas has claimed that Shiri Bibas and her children were killed by an Israeli airstrike, and called the IDF’s claims lies.

The Hostages and Missing Families Forum, which represents the families of those in Hamas captivity, said after the wrong remains were sent, “We are horrified and devastated by the news that their mother, Shiri, was not returned — despite the agreement and our desperate hopes.”

A spokesperson for the IDF said that military representatives were in contact with the Bibas family, and that reports that a new body has been released were under review.