A U.S. service member died of wounds inflicted by an explosive device outside of the city of Mosul in Iraq, the Pentagon said in a release Saturday.

The release from the U.S.-led coalition gave no other details, and a Pentagon spokesman was unable to elaborate. It is unclear whether the blast was combat-related. Mosul has been the site of heavy fighting since October as Iraqi forces have attempted to rout the Islamic State from the city.

Saturday’s death, if caused by hostile fire, would be the fifth U.S. combat death in Iraq since the start of the campaign against the Islamic State there in 2014, and the first during the Trump administration. In October, Navy Chief Petty Officer Jason C. Finan was killed by a roadside bomb on the outskirts of Mosul just days after the battle to retake the city began.

There are more than 5,000 U.S. troops in Iraq assisting the country’s military in its fight against the Islamic State. Some of the U.S. forces are in roles that bring them close and sometimes to the front lines. The Pentagon has stressed that the U.S. military is not directly fighting the Islamic State on the ground, instead saying the troops are in fire support and advisory positions. Often, however, U.S. troops are spotted on the front lines calling in airstrikes and assisting local forces.

The Islamic State seized Mosul in June 2014, and it has fought doggedly to retain the group’s largest stronghold in Iraq. Iraqi troops, backed by U.S.-led air power, have been forced to clear the city from east to west. The city’s labyrinth of small streets, alleys and rooftops has proved to be a boon for Islamic State fighters, helping them launch a relentless number of ambushes, suicide vehicle bombings and sniper attacks against advancing Iraqi soldiers.