The Pentagon on Thursday significantly raised its estimate for the number of civilians killed in U.S.-led coalition airstrikes in Iraq and Syria, admitting there were an additional 54 deaths that occurred between March 31 and Oct. 22.

The announcement brings the total of U.S.-acknowledged civilian casualties to 173 since the coalition began strikes against the Islamic State in the region during the summer of 2014. The release of this latest report comes less than a month after the last one, suggesting that the U.S.-led campaign is responding to critics who say that its investigations into civilian casualties have taken too long. Col. John Dorrian, the spokesman for Operation Inherent Resolve, said that the plan is to now release the casualty reports monthly.

On Nov. 9, U.S. Central Command said it had killed 64 civilians from November 2015 to September 2016. In July, the Pentagon said there had only been 55 civilian deaths since the start of the campaign.

Advocacy groups that track the U.S.-led airstrikes estimate civilian casualties to be significantly higher and say that the government too often discounts reports from local media outlets and activists on the ground.

With a small ground presence, the U.S.-led campaign is often unable to verify how many people have been killed by a strike except through self-reporting from pilots and surveillance footage. According to Thursday’s statement, the U.S.-led campaign “assesses all incidents as thoroughly as possible” by using  “traditional investigative methods . . . and analyzes information provided by government agencies, nongovernmental organizations, partner forces and traditional and social media.”

Thursday’s release found 12 reports received in October to be “noncredible.” Those 12 reports span from Sept. 20, 2015, to Oct. 6, 2016. Seven reports, including some received before October, were found to be credible, while three remain under investigation.

Of the seven credible reports, one stated that on July 18, 2016, up to 24 civilians were killed in a single strike in northern Syria. The date coincides with a highly publicized bombardment that took place overnight from July 18 to July 19 around Tokhar, a village just northwest of the city of Manbij. Activists claimed the strike, carried out by waves of A-10 attack aircraft and a massive Cold War-era B-52 bomber, killed roughly 100 people. Syrian activists said roughly 50 of the dead were civilians seeking shelter from the fighting, while the Pentagon claimed to have struck Islamic State fighters preparing to launch a counterattack on Kurdish and Arab fighters on the town’s outskirts.

Pictures posted to social media in the hours after the strike showed dead women and children.

Thursday’s statement on the July 18 airstrike said that “no civilians have been seen in the 24 hours prior to the attack,” and that reports indicated approximately 100 Islamic State fighters were in the area.

“Unknown to coalition planners, civilians were moving around within the military staging area, even as other civilians in the nearby village had departed over the previous days,” the statement said.

It is unclear whether the civilians killed were being used by the Islamic State as human shields, a tactic that the terrorist group has used extensively in recent weeks as Iraqi forces have slowly entered Mosul, Iraq’s second largest city and their largest stronghold in the country since it was seized in 2014. According to Chris Woods, director of Airwars, a Britain-based organization that tracks allegations of civilian deaths, coalition airstrikes have slowed significantly as Iraqi soldiers and Islamic State fighters are often located within yards of one another.

But while much of the focus remains on Mosul, Woods said that the majority of the civilian casualty reports he has seen in the last month have come from predominately around Raqqa, the Islamic State’s de-facto capital. In early October, Secretary of Defense Ashton B. Carter said that U.S.-backed Kurdish and Arab forces, known as the SDF, had begun the arduous task of encircling the city. Woods said those operations — and their supporting airstrikes — have created far higher civilian casualties than anything around Mosul recently. With reports still coming in, Woods was hesitant to give specific numbers.

The only U.S.-acknowledged deaths in Iraq during October were near the town of Fasitiyah. Eight civilians were killed when aircraft struck a building containing Islamic State fighters, the statement said. 

At the start of the U.S.-led air campaign, Centcom had released partially redacted investigations into errant airstrikes. It no longer does so. Instead the investigations are now likely only to be released through Freedom of Information Act requests.