The Nepali Army has located the crown, or uppermost section, of a tunnel at the Upper Trishuli 3A Hydropower Project, where dozens of people are feared trapped following Wednesday’s devastating flood.

According to Nepali Army spokesperson Rajaram Basnet, an army team working continuously for the past three days located the tunnel's upper section on Sunday afternoon.

A joint team of experts used drilling machines, excavators and hydraulic cutters to reach the crown head of the tunnel.

“After drilling a hole, we found that the water level extends high up inside a tunnel with a diameter of around seven metres,” Basnet told Kantipur.

Rescuers entered the tunnel through the opening after drilling through the crown section, according to Prime Minister Balendra Shah's secretariat. However, there was no response when the rescue team called out.

“Work is now underway to bring in larger equipment, carry out blasting and widen the opening to make the rescue operation easier and faster,” the secretariat said.

Military officials estimate that at least 35 people may be trapped inside the tunnel. The figure was provided following a technical assessment, although Nepal Police has put the number of people believed trapped at around 200.

The government has sought assistance from Indian and Chinese experts as the Nepali Army’s equipment and personnel are deployed across multiple disaster-hit areas.

Basnet said, however, that only the Nepali Army was involved in the operation at this particular tunnel.

The army also has personnel trained in disaster rescue operations in India, China and the United States.

A Chinese team arrived in Kathmandu on Saturday with thermal cameras, drilling equipment and air-pumping devices and is preparing to provide specialist assistance in search and rescue operations at hydropower tunnels that remain inaccessible.

India has also sent a team from the Indian Air Force with specialised equipment, along with experts for DNA collection. Military sources said teams from both countries had already conducted reconnaissance of hydropower projects that rescuers have yet to access.

“The Chinese team is being deployed at Hakubesi, while the Indian team is at Syafrubesi,” a military source said. The teams were preparing to begin work on Sunday.

By 3 pm on Sunday alone, the Nepali Army had rescued 409 people, including 15 Chinese nationals and one Indian citizen, from flood-affected areas.