House lawmaker and UN experts are calling for an “immediate” investigation into the strike on an elementary school in Minab, Iran, that massacred 175 people, mostly children, as a growing body of evidence suggests that U.S. forces were responsible for the strike.

“There needs to be an immediate and transparent investigation into this strike. I’m demanding answers on what is being done to protect innocent civilians in Iran,” said Rep. Yassamin Ansari (D-Arizona) in a post on X on Thursday.

A group of seven UN human rights experts also signed a statement on Friday saying that the strike must be investigated as a war crime.

“A strike on a school represents a grave assault on children, on education, and on the future of an entire community,” the experts said. “An attack on a functioning school during class hours raises the most serious concerns under international law and must be urgently, independently, and effectively investigated, with accountability for any violations.”

Iranian health officials and state media have reported that 175 people were killed in the strike on the school on February 28, as the U.S. and Israel unleashed their first bombardment of their war on Iran. The vast majority of them were children aged between 7 and 12, UN officials have said. One of the victims was reportedly a 2-month-old baby.