The Afghan government has tried to regulate the mining sector by offering new contracts in an effort to improve oversight, but even those deals have been marred by charges of corruption and irregularity.
Last year, the government in Kabul signed two contracts for exploration of copper and gold in the north. But watchdog groups criticized the agreements, saying they may violate conflict-of-interest laws and allow questionable practices that have marred the mining sector for years to continue.
Part of the river in Badakhshan where the deadly episode occurred is controlled by the Taliban, who get a cut from the gold panned there, said Mr. Talat, the provincial council member.
Separately, in the south of the country, the Taliban seem to have increased their attacks in recent weeks, officials said, and the official toll from an assault on Friday in Kandahar Province more than doubled by Sunday.
After the Taliban attacked a border police outpost in the district of Spinboldak on Friday, the local government put the number of soldiers killed at seven. But on Sunday, Nimatullah Wafa, a member of provincial council, confirmed reports attributed to local officials that 16 soldiers had died.
It was the latest in a series of attacks on police checkpoints in Spinboldak, which borders Pakistan. The district was also home to the former powerful police chief of Kandahar, Gen. Abdul Raziq, who was assassinated in a daring Taliban attack in October, barely missing Gen. Austin S. Miller, the top American commander in Afghanistan.
Officials have expressed fear that the Taliban will make a stronger push for Kandahar Province. Mr. Wafa, the provincial council member, said the insurgents had gained more influence in districts along the border with Pakistan and had launched more frequent attacks in areas that were once peaceful.
“The security situation in some Kandahar districts is getting worse,” Mr. Wafa said. “They have more courage to attack a peaceful district like Spinboldak — that rarely happened when General Raziq was alive.”