If confirmed, the killings would mark the deadliest bout of violence in years to hit a far-flung region wracked for decades by a low-level independence insurgency.
Citing local police, Indonesian media reported late on Monday that the workers were shot dead on Sunday in Nduga, a district in the centre of the region on the western half of New Guinea island, just north of Australia.
Police and military teams were sent to the area on Monday when they came under rebel gunfire with one soldier killed and another wounded in the firefight, authorities said.
The employees of state-owned contractor Istaka Karya were building bridges and roads as part of efforts to boost infrastructure in the impoverished region.
All construction work in the area would be temporarily suspended, the public works ministry said.
More than a dozen coffins were being readied in Wamena, the nearest major town to where the alleged killings happened.
“Some media are saying 31 workers are dead, some 24, so we really need to check ourselves,” said Papua military spokesman Muhammad Aidi.
A team of about 150 personnel would delay its operation until Wednesday morning, fearing a confrontation with rebels at night, the military said. “We think they’ll be expecting us,” local military chief Jonathan Binsar Sianipar said.
Four workers — including three suffering gunshot wounds — were among 12 civilians evacuated from Mbua district about 6pm on Tuesday, the Indonesian military said.
The violence was reportedly carried out by rebels who have long fought against Jakarta’s rule and were angry at some workers taking pictures of pro-Papua independence activities. Indonesia routinely blames separatists for violence in Papua.
Foreign media need permission to report from Papua and obtaining reliable information is difficult.
Authorities would “chase these criminals wherever they are”, said national police spokesman Mohammad Iqbal.
“But we need to check whether it was really (the rebels) or not,” he added.
The suspected killings could be the worst outbreak of violence in a “very, very long time”, said Sidney Jones, director of the Jakarta-based Institute for Policy Analysis of Conflict (IPAC).
“Every time we have had a significant incident that has involved military deaths, even though the main victims here were civilians, it is followed by massive retaliatory response,” she added.