New Delhi, Sept. 19: The headquarters of a forward-deployed army brigade in charge of manning the sensitive border with China in North Sikkim has all but fallen out of the military communication network in Sunday evening’s earthquake.

The army has a dedicated secure communication network. But the snapping of connectivity indicates just how jolted it was when the Richter indicated 6.9.

Two soldiers of a unit under the brigade who were killed in the quake were acclimatising at the Zima Transit Camp before being sent to posts between 9,000ft and 16,000ft. Two workers of the Central Public Works Department who were building a military road were also killed.

The headquarters of an Indo-Tibetan Border Police (ITBP) battalion in Pangong has been damaged.

The director general of ITBP, Ranjit Sinha, said here this afternoon that ITBP troopers rescued about 40 people from a village in the valley near Pangong and gave them blankets, food and shelter overnight.

Sources in the army here said there was only intermittent satellite communication with the headquarters of the 112 Brigade near Mangan. Mangan is the district headquarters of North Sikkim, the largest of the state’s districts that covers half its area. It has a population of less than 50,000.

The lack of voice and data communication meant that damage-assessment is just mostly guess work for now.

Units of the 112 Brigade man a wide front with China that includes the “Finger” area, a part of the state that juts into Chinese territory, from where repeated “transgressions” of the border were reported in 2008 and 2009. Since then, the Indian army has reinforced its defences in the front and has inducted tanks and armoured personnel carriers in the high plateau.

The sources said that landslides triggered by the quake have made it impossible for vehicles to transit between Gangtok and Mangan. There is also no communication between Mangan and Chumthang, where National Highway 31A forks for Lachen and Lachung.

The army is deployed all across North Sikkim. The Central Public Works Department and the Border Roads Organisation maintains the roads, that were widened in the last two years, largely to make deployment of military vehicles faster in the event of an emergency.

The brigade is under the 17 Black Cat Division headquartered in Gangtok but also shares operational responsibility to a brigade under the 27 Mountain Division headquartered in Kalimpong.

“We have difficulty maintaining communication with 112 even when the weather is bad but this is more serious,” one officer said. Incessant rain has also made frequent helicopter sorties difficult. Even in normal times helicopters usually do not fly in the heights after 3pm. Many of the frontier posts are “air maintained”, meaning they are dependent on supplies and reinforcements by helicopter.

The earthquake has also wrecked a project of the CPWD to build three roads for the army from Lachen and Lachung towards the China border. The two workers who were killed were staying in a CPWD camp about 30km from Lachen. The other officers are said to be safe. The CPWD started the work on three roads in Sikkim this year itself.

Till late this evening, none of the disaster-relief teams – including National Disaster Response Force and some 5,000 troops of the army -- sent from Delhi and stations in the plains was able to reach North Sikkim.