NATO is investigating a possible friendly-fire incident on Monday that led to the deaths of five American troops in Afghanistan.

If the attack in southern Afghanistan is determined to be related to friendly fire, as an Afghan official reported to CNN, then the incident will be among the deadliest NATO friendly-fire attacks in Afghanistan since the war started in 2001.

Here’s a look at some of the deadliest friendly-fire attacks in Afghanistan:

1) November 26, 2011

In the attack known as the Salala incident, U.S.-led NATO troops killed 24 Pakistani soldiers who were sent to the border of Pakistan and Afghanistan to hunt down militants. The NATO troops crossed the Afghanistan side of the border during the incident and fired on the soldiers using Apache helicopters, two fighter jets and a gunship. The Pakistani soldiers were stationed at military checkpoints on the border.

The friendly-fire incident angered the Pakistani government, which cut off NATO supply lines through Pakistan as a result. Nearly nine months after the incident, Pakistan restored the supply lines following an apology from then-U.S. Secretary of State Hillary Clinton.

2)      April 9, 2010

Six Afghan troops were killed by German soldiers who fired on two civilian vehicles that were transporting them.

The German soldiers fired after the vehicles didn’t obey an order to stop. The Germans were on their way to fight Taliban insurgents in Kunduz in northern Afghanistan.

3)      April 8, 2002

In what became known as the Tarnak Farms incident, an American fighter jet dropped a bomb on Canadian soldiers who were conducting a military exercise near Kandahar, killing four and injuring eight. The deaths marked the first of any Canadian soldiers in a combat zone since the Korean War.

Maj. Harry Schmidt of the Air National Guard apologized for dropping a 500-pound bomb on the Canadian soldiers and said he believed the Taliban was planning an ambush around Kandahar.

"I would like to say first and foremost that I sincerely regret the accident that occurred ... My heart goes out to the families of the men killed and injured in what can only be described as a tragic accident in 'the fog of war'. The accident was truly unfortunate and I am sorry that it happened,” he said. "I was called upon to make a perfect decision in a rapidly unfolding combat environment. I had to make that decision with what I now know, with the acuity of 20/20 hindsight, was imperfect information ..."

4) January 12, 2008

Dutch troops killed two of their own and two Afghan soldiers. Gen. Dick Berlijn, the top Dutch military commander at the time, said bad weather during a night battle led the troops to mistake friendly troops for the enemy.

“Darkness, the weather conditions and the confused situation,'' played a role in the friendly-fire incident, Berlijn said, according to the Associated Press.

5) December 9, 2008

Six Afghan police officers were killed by U.S. forces in southern Afghanistan after a “tragic case of mistaken identity” on both sides, according to the New York Times.

American forces overran a hide-out of a suspected Taliban commander, killing the commander and detaining another person, when they were fired on by Afghan police officers.

The Americans returned fire with small arms and aircraft, but they didn’t realize they were shooting at police officers until the firefight ended.

“Coalition forces deeply regret the incident of mistaken fire,” a military spokesman said at the time. “Initial reports indicate this was a tragic case of mistaken identity on both parts.”