KATHMANDU — A barrier lake perched above the Nepal-Tibet border briefly halted flood rescue operations Friday before water levels eased, as the death toll from Wednesday's Himalayan flash flood surpassed 500 and Nepal police warned rescue teams to stay on high alert for a possible dam burst on the Tibetan side.

The debris-dammed lake, which formed at the confluence of the Chhochen Khola and Purepu Tsangpo rivers, represents the disaster's most immediate secondary threat, with hundreds of trekkers and pilgrims from more than 30 countries still unaccounted for two days after a glacial collapse loosed the initial wall of water.

Toll rises

Nepali police put the confirmed dead at 489 as of Friday afternoon, with 977 people missing, the BBC reported. Agence France-Presse later placed Nepal's toll at 538. On the Chinese side, state broadcaster CCTV said five people had been killed and 558 remained missing. Nepal's disaster agency cautioned that some individuals could be counted on both national tallies. The Red Cross estimated 90,000 people had been affected by the flooding.

The lake

Rescue operations were briefly suspended Friday after the barrier lake overflowed, then resumed once water levels dropped, Chinese state media said. Beijing had warned there was a "high risk" of a fresh flood if the dam gave way. CCTV said the lake sits at 9,680 feet, roughly 3,280 feet above Gyirong Port — the border crossing struck Wednesday — and later described the flood risks as "manageable," Reuters said. Heavy rain is forecast for the coming days.

Foreign nationals

Nepal's government has released a list of more than 500 foreign nationals out of contact, including 178 Indians, nearly 100 Chinese, 65 Americans, 53 Ukrainians, 51 Malaysians traveling with Fishtail Tours and Travels, 39 Australians, 33 Britons and 24 Canadians, along with smaller numbers from South Korea, South Africa, Portugal, the Netherlands and New Zealand. The Isha Foundation, an Indian spiritual group, said about 80 of its pilgrims from 19 countries were missing.

Digging out

Nepali army rescuers were pulling mud-caked survivors from a hydropower tunnel at the Upper Trishuli-1 project in Rasuwa district, army spokesman Brig. Gen. Raja Ram Basnet told The Associated Press. Helicopters have carried more than 3,000 people to safety, CBS News reported. Nepal police spokesperson Abi Narayan Kafle said the rescue operation "hasn't stopped," and was proceeding under high alert.

The scale of the loss remains contested. Nepal's disaster management authority listed 977 missing on Friday, but local Nepalese media cited by CBS News have put the possible total as high as 12,000 — many times the official count. Officials have also warned that names could be double-counted between the Nepali and Chinese tallies.

Weather forecasters expect more rain across the region into the weekend. Chinese Premier Li Qiang, who arrived in Gyirong on Thursday to direct the response, remained on the border.