The Israeli military on Thursday acknowledged that troops mistakenly shelled a United Nations facility in central Gaza last month, killing a UN worker from Bulgaria.

Until now, the Israel Defense Forces had denied it had struck the compound.

According to the findings, on March 19, an IDF tank operating in the area fired a shell at the building, following a “suspicion of enemy forces in it.”

The investigation has found that the building was not identified by the tank crew as belonging to the UN.

Bulgaria said Thursday it had “received an official apology from Israel” over the incident.

Bulgaria’s Foreign Minister Georg Georgiev called for “such tragedies not to happen again,” stressing in a statement that “the protection of humanitarian workers is a top priority.”

The United Nations Office for Project Services (UNOPS) announced on March 19 the death of one of its employees in the central Gaza city of Deir el-Balah when an unidentified piece of “explosive ordnance” hit their building.

In light of the incident, the UN said it would take some 30 international staff out of Gaza, from a total of about 100.

The IDF’s high-level General Staff Fact-Finding Assessment Mechanism, an independent military body responsible for investigating unusual incidents amid the war, is looking into the event.

The mechanism’s initial findings were presented today to IDF Chief of Staff Lt. Gen. Eyal Zamir and UN representatives, the military said.

Zamir has instructed the head of the mechanism, Maj. Gen. (res.) Yoav Har-Even, to conclude the probe in the coming days and present the full findings to the UN representatives.

The IDF said it “regrets this serious incident and continues to conduct thorough review processes to draw operational lessons and evaluate additional measures to prevent such events in the future.”

“We express our deep sorrow for the loss and send our condolences to the family,” the military said.