Authorities on Saturday discovered a 400-meter long tunnel, running between India and Pakistan, along the International Border in Samba district of Jammu and Kashmir.

"We have discovered a tunnel running between Pakistan and India in Samba district," Senior Superintendent of police (Samba) Israr Khan told reporters.

The tunnel was detected after an area caved-in at two or three places due to rains near the Border Security Force's Chillayari Border Out Post, he said.

"After the cave-in, the area was dug out to know the reason. But, the authorities were surprised to find a tunnel," the SSP said.

The tunnel, with a dimension of 3x3-ft, was running between Chillayari BOP and Pakistan's Numberiyal BOP, he said. Dug at a depth of 25-ft below the ground level, it was 400-mt long on the Indian side, the SSP said adding, "We are confirming whether the tunnel is operational or not."

The tunnel, which seemed to be freshly constructed, had air supply through a 2-inch pipe, he said adding 'we are looking into all aspects'.

Pakistan must be facing a lot of pressure from the terrorists to infiltrate them into the Indian territory, the SSP said. "Since it is difficult to push in terrorists to the Indian side, they decided to set up a tunnel to facilitate infiltration," the SSP said.