A 400 - meter underground tunnel was unearthed along the India-Pakistan border in Indian-controlled Kashmir, officials said Sunday.

The tunnel was unearthed Saturday in frontier district of Samba, around 50 km southwest of Jammu, the winter capital of Indian- controlled Kashmir.

"A tunnel was detected after an area caved in due to rains near the Border Security Force Chillayari border outpost," Israr Khan, the Senior Superintendent of Police, Samba told reporters.

Khan said the tunnel with four feet diameter is running between India's Chillayari border outpost and Pakistan's Numberiyal border outpost.

The tunnel was first detected by a local villager during routine visit to his fields. The villager informed the Indian border guards of BSF deployed in the area, following which they started excavation.

Reports said the subsequent digging unearthed a tunnel 20 feet deep from the earth's surface, laid with oxygen pipes.

Police and BSF authorities have started investigations in this regard.