U.S. military airstrikes are believed to have been responsible for the deaths of 200 civilians in Mosul, Iraq.
The New York Times reports that the March 17 attack ranks among the highest lost of civilian life in a single air attack since the U.S. military invaded Iraq in 2003.
But the U.S. military hasn't ruled itself responsible just yet. U.S. Central Command spokesman Col. John J. Thomas said that the military was trying to figure out if the deaths were the result of U.S. airstrikes or a bomb or booby trap placed in the area by Islamic State militants.
"It’s a complicated question, and we’ve literally had people working nonstop throughout the night to understand it," Thomas told the New York Times, adding that the explosion and the reasons behind it had "gotten attention at the highest level."
Meanwhile, Iraqi officers working in tandem with the U.S. military have blamed the Islamic State for the civilian loss of life.
Maj. Gen. Maan al-Saadi, a commander of the Iraqi special forces, said that his troops called in a U.S. airstrike to take out three Islamic State snipers believed to have been on the roof of a complex in the area.
"After the bombing we were surprised by the civilian victims," the general said, "and I think it was a trap by ISIS to stop the bombing operations and turn public opinion against us."
Whatever the cause for the massive civilian deaths during the Mosul strike, observers say there has been a sharp increase in civilian deaths overall in recent months.
Chris Woods, director of Airwars, a nonprofit group that monitors the numbers of civilian deaths as a result of U.S. and coalition airstrikes in Iraq and Syria, told the New York Times that March's civilian deaths totals have already reached 1,058, compared to 465 in December.
"We don’t know whether that’s a reflection of the increased tempo of the campaign or whether it reflects changes in the rules of engagement," Woods said, but added that the increase "does suggest something has shifted."
But Pentagon spokesman Capt. Jeff Davis denied that suggestion.
"There’s been no loosening of the rules of engagement," he said.
In a statement, U.S. Central Command acknowledged the civilian casualties.
"The Coalition respects human life, which is why we are assisting our Iraqi partner forces in their effort to liberate their lands from ISIS brutality," the statement read. "Our goal has always been for zero civilian casualties, but the Coalition will not abandon our commitment to our Iraqi partners because of ISIS's inhuman tactics terrorizing civilians, using human shields, and fighting from protected sites such as schools, hospitals, religious sites and civilian neighborhoods."