Five American troops were killed on Monday in central Iraq, U.S. officials said - the single largest loss of life for the American military in Iraq in the past two years.

The military said in a brief statement that the five were killed on Monday, giving no additional details about where the incident occurred or how they died.

The incident was under investigation and the names of the deceased were being withheld pending notification of the next of kin, the military said.

The deaths raised to 4,459 the number of American service members who have died in Iraq, according to an Associated Press count.

The U.S. currently has roughly 46,000 U.S. troops in Iraq, down from a one—time high of roughly 170,000. The American military officially ended its combat operations in Iraq last August and reduced its forces to less than 50,000 troops.

The remaining forces are focused on training and assisting Iraqi security personnel, and are not supposed to be actively engaged in combat operations. However, American forces still come under almost daily attack by rockets and mortars in their bases and get shot at and targeted by roadside bombs when they move outside of their bases.

Monday’s incident was the single largest loss of life for the U.S. military since May 2009, when five U.S. troops were killed in Baghdad during a non—combat related incident. In April 2009, six U.S. troops died - five in combat in the northern city of Mosul and one north of Baghdad in a non—combat related incident.

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