Iranian security forces may have killed more than 1,000 people since protests began over the government’s decision to raise fuel prices, according to a top State Department official.

“We can’t be certain because regime blocks information,” U.S. Special Representative for Iran Brian Hook told a press conference at the State Department.

At least a dozen children, including 13- and 14-year-olds were killed, said Hook.

He also said the State Department has seen a video of one incident in which more than 100 people were killed.

“When it was over, the regime loaded the bodies into trucks.

Read more: Over 1,000 may have been killed in Iran protests: US