OTTAWA—A Kurdish militia soldier reported that an airstrike by Canadian fighter jets in Iraq in January may have killed up to 27 civilians, U.S. documents say.

The peshmerga soldier told coalition special forces that a Jan. 21 strike by CF-18 fighters near Mosul may have killed between six and 27 bystanders.

The Canadian military says it didn’t investigate the claims because it found no supporting evidence and continues to insist it has no proof that any civilians died in the attack.

The reports of possible civilian casualties are detailed in an internal document titled “allegation tracker” prepared by U.S. Central Command to log and review reports of civilian casualties in the ongoing, multinational air campaign against Islamic State fighters in Iraq and Syria.

The documents were obtained under U.S. Freedom of Information legislation by journalist Joseph Trevithick for the blog site War Is Boring.

They were shared by the Airwars project, which has sought to track civilian casualties in Iraq and Syria in the air war against the Islamic State.

The details of the documents were first reported by CBC News on Thursday.

Canadian CF-18s fighters have been conducting air strikes against Islamic State targets in Iraq since last November, a campaign that was expanded to Syria in the spring.

At the time, Kurdish forces were launching a major offensive to capture this key junction.

British journalist Chris Woods, who leads the Airwars project, said it’s significant that a Kurdish soldier made the report of the casualties.

“This report didn’t come from a bystander or a Tweet or social media. It came from an English-speaking fighter working with the coalition . . . who makes a fairly clear allegation,” Woods told the Star in an interview.

“And that this came through special forces, who obviously gave this individual credibility as well,” he said.

Yet the Canadian military told the U.S. military they saw no obligation to examine what happened. “It should be noted that (Canadian Joint Operations Command) legal opinion is that under the Law of Armed Conflict (LOAC) there is no obligations for the (Canadian Armed Forces) to conduct an investigation,” the U.S. document states.

The Canadian military declined to make anyone available to speak to the Star on the issue Thursday. However, in a statement, the military said that coalition headquarters reviewed photos and video and “uncovered no evidence of civilian casualties” resulting from the bombing.

“It was reconfirmed that the target struck by Canada was a valid military objective,” the statement said.

A separate review by the Canadian military also turned up “no substantive grounds” to believe civilians had been killed, it said.

Still, NDP candidate Jack Harris called the report “concerning” and said the new details should prompt Defence Minister Jason Kenney to order a full investigation.

“I’m not satisfied that this government has acted properly and the minister has been doing his job,” Harris said in an interview.

Canadian military officials repeatedly denied that Canadians strikes had caused any civilian casualties even as, behind the scenes, questions were being raised about the January strike.

“Canada is quite confident that with all the strikes that we’ve executed, there is absolutely no evidence of civilian casualties associated with our strikes,” navy Capt. Paul Forget told a briefing in July.

At the same briefing, Forget said the coalition forces take efforts to minimize the chance of civilian casualties.

“Ultimately the last decision lies with our highly trained pilots who have that last focus, if you will, last eyeball, on the target to make that decision of whether or not ordnance is dropped,” Forget told a briefing in July.

Woods called the document “unexpected.”

“We are not used to seeing this level of detail during a conflict,” he said.

The documents relate possible civilian casualties caused by other strikes as well. Woods said in a number of the incidents, military officials dismissed allegations of civilian casualties within 24 to 48 hours “almost always based on aerial assessment.”

“To make these kinds of instant assessments is not helpful,” Woods said, noting it can often take days to get reports of casualties from the battle zones.

“At times this feels more like bookkeeping than credible casualty investigation,” Woods said.

However, he noted too that several occurrences of civilian casualties were reported by the military forces themselves.