(NewsNation) — Questions have emerged Monday about the possible involvement of Iran in the attack against Israel.

The Wall Street Journal quoted unnamed senior members of Hamas and Hezbollah saying Iranian security officials helped plot Hamas’s surprise attack on Israel on Saturday and gave the go-ahead for the assault at a meeting last Monday in Beirut. Hamas leaders told the outlet that Iran’s Islamic Revolutionary Guard Corps had coordinated with Hamas since August on attack plans.

A senior defense official tells NewsNation that Iran is in the picture and has provided support to Hamas for years, but the Biden administration doesn’t have specifics that corroborate the Wall Street Journal’s reporting at this time.

Iran has reportedly denied involvement. Ali Barakeh, a member of Hamas’ exiled leadership, told The Associated Press the attack was planned by around a half dozen top Hamas commanders in Gaza and that some of the group’s closest allies did not know about it in advance. Barakeh rejected reports that Iranian security officials assisted in planning the attack or greenlighted it.

Hamas launched the surprise attack on Israel over the weekend. Israel formally declared war Sunday. The war’s death toll has risen to nearly 1,600 on both sides. U.S. officials confirmed at least 11 Americans are among the dead.

The Associated Press contributed to this report.