Hamas began constructing its headquarters under Shifa Hospital, Gaza’s central hospital, from the moment the organization took control over the Gaza Strip in 2007, the New York Times reported on Monday, citing eight former and current IDF and intelligence officials. The organization first dug additional levels under the hospital’s basement, after which it connected it to its tunnel system, which runs under Gaza.

A senior Shin Bet official told the NYT that Hamas’s complex includes several floors, which contain meeting rooms, barracks, and storage. According to the report, several hundred people at least can gather in these spaces. A statement by the IDF Intelligence Directorate to the newspaper stated that Hamas terrorists divert electricity from the hospital to the headquarters and that the headquarters have several entrances, both from within the hospital and from the outside.

The Israeli officials told the New York Times that in the past, the IDF refrained from operating in the hospital to prevent civilian casualties, but it paid a price for this since what is under the hospital has remained untouched. The officials said that Israel would not repeat that mistake and the Hamas complex under Shifa would not remain, despite international pressure to spare it and additional hospitals.

The Shifa Hospital has been one of the focal points of the international debate around the conflict. Israel has proven that while on its top floors, the hospital treats patients below ground, Hamas runs a central headquarters, hiding behind the civilians in the building.

On Sunday, the IDF revealed that it coordinated with hospital staff to transfer much-needed fuel for urgent medical use and even placed 300 liters of fuel at the entrance to the hospital, but Hamas officials prevented the fuel from reaching its destination.