JAKARTA (Reuters) – Indonesian soldiers on Thursday retrieved the bodies of nine construction workers killed by separatists in the province of Papua, where fresh fighting halted a search for the remaining dead, a military spokesman said.

Colonel Muhammad Aidi said efforts to retrieve more bodies from the weekend attack on a Papua construction site were halted after soldiers clashed with fighters from the separatist Free Papua Movement (OPM).

“We still haven’t been able to recover another seven because there was a shootout between the military and the separatist group,” Aidi said, adding that the bodies of 16 of the 19 workers killed in the attack had been located.

The nine bodies retrieved so far were flown to the town of Timika, he said. Most had gunshot wounds to the chest and head.

On Monday, members of the same separatist group attacked a military post near the construction site, killing one soldier.

A separatist conflict has simmered for decades since Papua was incorporated into Indonesia after a widely criticized U.N.-backed referendum in 1969.

In June, three bystanders were killed and a child wounded when Papua separatists fired at a plane transporting security personnel for regional polls.

“We will give the separatist group the chance to surrender and join Indonesia and we will make sure they are safe. If they resist, they will face our force,” Aidi said.

The OPM separatists said this week they viewed the construction workers as members of the military and casualties of a war against the Indonesian government.

Indonesia officials say the workers were civilians employed by state construction firm, PT Istaka Karya, which is building bridges for the Trans Papua highway, part of President Joko Widodo’s pledge to open up access to the resource-rich province.

On Thursday, Widodo said on his official Facebook page “this incident emboldened us to continue the great task of building the land of Papua”.

OPM spokesman Sebby Sambon said on Wednesday government efforts to develop the province had marginalized Papuans.

“We don’t need road construction from Indonesia. When we become independent we can make our own roads that are as good as the ones in developed countries,” he told Reuters by telephone.