White House spokesman John Kirby said the U.S. knows some of the Americans − a “very small” number − are being held hostage by Hamas but does not know their condition or location. He said the administration is doing “everything we can” to locate them and bring them home. The known death toll of Americans has risen to 22 Americans killed, and 17 Americans are still missing in Israel following the Hamas attack, the White House said Wednesday – and the figures could rise further.

“We don’t know if they’re all in one group or broken up into several groups. We don’t know if they’re being moved and with what frequency and to what locations,” Kirby said. “Tough to get more detail.”

Kirby said the U.S. is “casting the net wide” on hostage-recovery efforts, citing discussions with the Israeli government, other Middle East allies and countries such as Qatar that “that have open lines of communication with Hamas.”

At a kibbutz near Gaza, Major General Itai Veruv said the military found evidence of militants cutting the throats of bound captives, lining up children and killing them and packing 15 teenage girls in a room before throwing a grenade inside.Roughly 260,000 people have fled their homes from Gaza and are taking shelter in packed U.N. schools.

Rep. Michael McCaul, a Republican from Texas who’s the chairman of the House Foreign Affairs Committee, said the Hamas onslaught Saturday likely resulted from a “failure of intelligence” and that it was uncertain how both the U.S. and Israel were caught by surprise.

McCaul also claimed that “a warning was given,” but it wasn’t clear at what level of government. Israel Prime Minister Benjamin Netanyahu said he did not have any prior knowledge of the attack, calling those reports “absolutely false.”