South Sudanese lawmakers have accused the consortium running the country’s last working oil fields of dumping expired chemicals in the bush on Feb. 28, and have threatened to shut down production unless it stops.

Members of parliament’s energy committee told the assembly they had seen containers holding old chemicals including potassium chloride in a remote area in the northeast, saying locals feared for their health. Reuters could not immediately verify the assertion.

The DAR Petroleum Operating Co. (DPOC)—which runs the northeastern neighboring oil Blocks 3 and 7 near the borders of Sudan and Ethiopia—told Reuters it had no one available to comment.

Spokespeople and officials from the members of the consortium—China’s Sinopec and CNPC, Malaysia’s Petronas, South Sudan’s Nilepet and Egypt’s Tri-Ocean Energy—all declined to comment.

Any move to go through with the threatened shutdown would deal another heavy blow to South Sudan’s economy, which depends on its crude reserves for almost all its revenues and has already been battered by more than four years of civil war.

James Lual Deng Kuel, head of the energy committee, told parliament on Feb. 28 last week that members had found chemicals were being dumped 10 km (7 miles) from a village in a location known as the Gumry Expired Toxic Chemicals Yard.

The boxes were “left exposed to the winds and rains that might blow and carry the toxic material [away]”, he said.

The accusation and threatened action mark the first time South Sudanese lawmakers have moved to enforce standards on protecting the environment laid out in a 2012 law governing the oil industry.

The parliamentarians spoke to DPOC staff members at the site, according to a report submitted to parliament by the committee members, seen by Reuters.

The lawmakers told parliament they had seen 36 shipping containers filled with expired chemicals that they said had come over the border from Sudan. They provided photographs of sacks and containers and, in the report, said the chemical was potassium chloride that had expired in October 2016.

MP Susana Peter Machar told Reuters last week her delegation had also seen 14 additional shipping containers carrying expired chemicals arriving in Paloich by truck from Sudan.

She said that if the consortium did not halt what she described as dumping, “we will force them to shut down oil production and we are serious”.

The oil fields are the last still operating in the impoverished country after conflict shut down others and froze investment. They are estimated to produce about 130,000 barrels per day—a third of the country’s peak reached before the war.