Smoke billows after a reported airstrike by the U.S.-led military coalition on Feb. 3 in the area of east Ramadi, Iraq. (Ahmad Al-Rubaye/AFP/Getty Images)

The U.S. military has reopened its investigation into a 2015 airstrike near the Iraqi city of Mosul that killed at least 11 civilians, including nine women and children, U.S. military officials said.

The move by U.S. Central Command follows an article in The Washington Post that identified flaws in the initial probe of the attack, which concluded that only four civilians were killed.

The Post’s story also raised broader questions about the military’s efforts to investigate battlefield mistakes. In nearly two years of bombing and more than 12,000 airstrikes in Iraq and Syria, the U.S. military has acknowledged only 41 civilian deaths. Military analysts and human rights activists said those figures vastly understate the civilian casualties caused by U.S. airstrikes.

“There’s not a chance that number is right. Just equipment failures alone would have killed 41 civilians, not even accounting for far more common human mistakes or bad intelligence,” said Jason Lyall, an associate professor of political science at Yale University who studies the effects of air power and served as a technical adviser to the U.S. government in Afghanistan. “The lack of curiosity here is entirely alarming.”

If confirmed by military investigators, the 11 civilian deaths in the attack on the Islamic State checkpoint in the village of Hatra would account for more than 25 percent of all civilian casualties acknowledged so far by the U.S. military in Iraq and Syria.

An initial review of the strike by the Air Force found the allegations in The Post’s story “credible,” and Air Force officials, based in Qatar, have “since opened an investigation,” said Col. Patrick Ryder, a spokesman for U.S. Central Command.

Gen. Joseph Votel, who commands American forces in the Middle East and Central Asia, said that the U.S. military goes to “great lengths to target only our enemies.”

“We take allegations of civilian casualties seriously, including this new information about our strike at the ISIL checkpoint near al Hatra,” Votel said in a statement, using a common acronym for the Islamic State.

The White House is on the verge of releasing a long-delayed report on militants and civilians killed by the United States in countries where it is not at war. The list will include airstrikes in countries such as Libya, Pakistan, Somalia and Yemen. It will not include deaths in Iraq or Syria.

White House officials declined to comment on the deaths at the Hatra checkpoint, but National Security Council spokesman Ned Price said the United States goes to “extraordinary lengths to avoid noncombatant deaths.” In cases where civilians are wounded or killed, Price said that the U.S. military is authorized to make condolence payments “to those injured and the families of those killed.”

So far, though, in nearly two years of airstrikes, the U.S. military has yet to make any condolence payments, according to military officials.

The checkpoint strike near Mosul and subsequent investigation show why so few payments have been made and why the military’s civilian death count remains so low. U.S. military officials first learned of the possibility of civilian casualties in the strike when the U.S. Embassy in Baghdad received an email from a woman who said her Kia Sorento had been blown up by U.S. planes.

Raja’a Zidan al-Ekabee wrote that two families trying to flee Mosul, traveling in her Kia and a GMC Suburban, were killed when they were stopped at an Islamic State checkpoint in the town of Hatra.

“A missile of the international air forces struck the checkpoint and both cars with the families inside them were burned to death,” Ekabee wrote.

Because the cars were stopped at the checkpoint for 40 minutes, U.S. pilots told military investigators that they assumed the vehicles were allied with the militants and attacked them. Investigators reviewed footage from the strike last year and spotted four figures fleeing one of the burning vehicles just before a 500-pound bomb hit. Only by pausing the image and measuring the height of the shadows of the figures on the grainy black-and-white video did the investigators determine that one of the people was probably a child.

The military’s investigation, relying exclusively on the video footage, concluded that four civilians were killed in the strike. Such footage, however, can be unreliable. A recent study conducted by CNA, a federally funded think tank, concluded that bomb damage assessment videos in Afghanistan had missed civilian deaths in 19 out of 21 cases that were later investigated on the ground.

The military never tried to contact Ekabee to determine who was traveling in the cars that were destroyed at the checkpoint. If they had called her, they could have learned that the dead included the family of an Iraqi police lieutenant colonel who were trying to escape Islamic State-controlled Mosul. In an interview with The Post, the lieutenant colonel said that his wife, 9-year-old daughter and two sons, ages 10 and 16, were killed, along with the driver of the car.

“I just want to be left alone in my misery,” he said in the interview more than a year after the airstrike.

Those killed in the second car included the driver, his grandmother, aunt, sister and two children.

The U.S. military said it is constrained in its ability to investigate civilian deaths from American airstrikes because it has so few troops on the ground in Iraq and Syria. “We recognize that we are not perfect and there are things we may not see,” Ryder said.

Military officials said they take great care in their targeting process to ensure no civilians are injured or killed. “The amount of effort that goes into trying to avoid civilian casualties is probably about the same, if not more laborious, than the actual targeting process itself,” Ryder said.

The United States monitors Iraqi media and works with the State Department and nongovernmental organizations to seek out allegations of civilian deaths.

But the process for logging and investigating complaints in Iraq and Syria is flawed, human rights activists said. “When I met with senior U.S. military officials in Tampa a few weeks back, they admitted that they had only assessed 40 percent of all 430 known alleged coalition civilian casualty events — an omission we hope they are tackling,” said Chris Woods, the director of Airwars.org, an organization that tracks civilian casualties in Iraq and Syria.

One airstrike that was never logged or investigated took place in the northern Iraqi town of Bashiqa on Nov. 24

Massoud Hameed said in an interview with The Post that his brother and sister-in-law and their three children were killed when an airstrike hit their home in the village. His local parliamentarian said he complained to the U.S. Embassy about the deaths, which were also reported in the Iraqi media and logged by Airwars.

The U.S. military recently said it had no record of a civilian casualty allegation in Bashiqa.

Woods called the oversight “troubling.”

“For the coalition to say it was unaware of the civilian casualty event despite [media] reporting, a complaint to the U.S. embassy and an Airwars case study is bizarre, though not unexpected,” he said.