It was a cargo 737 which shows the following cargo capacity:
Boeing 737-200 6LD7 +Bulkhold 70.0m3 19,500 kg
Could it have been carrying fuel in to the airport?
BTW - the airport has some 'interesting' history:
Accidents and incidents[edit]
Wamena airport, the only airport in the region that can accommodate the Indonesian Military (TNI)s Hercules airplanes, was razed by fire on September 26, 2011; all buildings including the departure and arrival terminals were engulfed by fire.[6]
On April 21, 2002 an Antonov An-72 (ES-NOP) of Estonian airline Enimex was damaged in a hard landing at Wamena Airport; a minor fire broke out. Due to the dead battery of the fire truck some firefighters ran to the accident scene with hand-held fire extinguishers. After some 20 minutes the truck's battery was charged, but the aircraft had to be written-off. There were no fatalities.[7]
On December 18, 2016, an Indonesian Air Force C-130H Hercules flew into hills 1700 m southeast of the runway threshold while attempting to land in poor visibility, killing all 13 on board.[8][9]