Three U.S. service members were killed and another three were wounded by an improvised explosive device in Afghanistan on Tuesday.

Officials said an American contractor was also wounded. Those injured were evacuated and are receiving medical care.

The identity of those killed will be released after their next of kin has been notified.

The Pentagon has announced the deaths of 28 U.S. service members in 2018. The latest deaths bring the number of U.S. troops who have died in Afghanistan to 13. Eleven of those have been from hostile fire in combat or from an insider attack. One service member has died from friendly fire, another service member died in a noncombat incident.

More than 2,400 service members have died in Afghanistan since the start of the 17-year war, America’s longest conflict.

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