The Israeli military says it has discovered tunnels underneath the main headquarters of the U.N. agency for Palestinian refugees in Gaza City, alleging that Hamas militants used the space as an electrical supply room.

The unveiling of the tunnels marked the latest chapter in Israel’s campaign against the embattled agency, which it accuses of collaborating with Hamas.

Recent Israeli allegations that a dozen staff members participated in the Hamas attack on Israel Oct. 7 plunged the agency into a financial crisis, prompting major donor states to suspend their funding as well as twin investigations. The agency says that Israel has also frozen its bank account, embargoed aid shipments and canceled its tax benefits.

The army invited journalists to view the tunnel on Thursday.