An Israeli military official said a "very big" drone was used in an attack on Tel Aviv on Friday that killed one person, and "human error" led to the missile not being intercepted.
Yemen's Houthi rebels claimed responsibility for the attack that caused an explosion at a building near the US embassy in Tel Aviv.
The military official told a briefing that an attack by the Iran-backed Huthis was "one of the possibilities" being investigated.
The official, speaking on condition of anonymity, said "a very big drone that can travel long distances" was used in the attack which was at 3.12 am (0012 GMT).
He said the drone "crashed into an apartment building" and "it wasn't a tiny drone".
The official said the aim was "terrorism". "Their main goal was to kill civilians in Israel."
The official said the drone was detected but the alarm was not immediately raised because of "human error".
"There was no alert that sounded in Tel Aviv because it wasn't activated.
"There was a human error that caused the interception and defence systems not to be operated," the official said.
"Obviously, one of the possibilities we're looking into is Yemen because of the Huthi announcements. But we're not ruling out anything."
The official said another drone was detected on Israel's eastern border.
"Last night, there was another incident where we thwarted a UAV on our eastern border, another UAV." He gave no details on where it came from.
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