The National Highway-707 was blocked near Sataun area of the district, following a landslide on Sunday.
The region has been witnessing relentless rain in the last two days.
"The road sunk at Kachi dhank near Sataun in Sirmaur district. Around 200 metres of the road in the area sunk in by several feet in the area," Anil Sharma, Executive Engineer of National Highway Authority of India said.
NH-707 connects Poanta in Sirmaur district to Hatkoti in Shimla district. The place where the road sunk in is nearly 165 km from state capital Shimla. This is the shortest route for the people of the district to reach Dehradun and New Delhi.
The national highway was blocked today afternoon at around 2 pm, hampering all kind of vehicular traffic.