A tunnel that starts in Pakistan and can enable infiltrators to crawl 300 metres into Indian territory was detected on Saturday on the international border in Samba district, 70 km from Jammu.
SSP Samba Israr Khan said the BSF personnel guarding the BoP observed that fields has caved in about three-feet.
He said, on closed observation it was found that it had caved in a three different places in a straight line, leading to suspicion.
The police official said they also found a plastic pipe, which it is believed to be have been used or was to be used for oxygen supply to intruders.
He said on Saturday morning BSF personnel put in JCB machine to dug in the area and after digging in about 25- feet they found three feet-by-three feet tunnel.
Across the Chachwal BoPs is Lambrayl post in Shakargarh tehsil of Pakistan. BSF officials refused to talk on the matter and didn't allow the media to reach the site.
The tunnel was dug in beneath the border fence, which is about 300mt inside the Indian territory.
He said the BSF personnel are still trying to find out the opening of the tunnel.
SSP said it cannot be said with certainty if the tunnel has been used in past to infiltrate terrorists, till the opening is found.
According to police sources, a local working in the fields' found the caving in of the fields and a plastic pipe on Friday evening and reported the matter to BSF.
Meanwhile, security has been tightened in the area after the detection.