Jammu: Over 71,000 pilgrims have performed the Amarnath Yatra so far as another batch of 1,612 pilgrims left Jammu on Thursday. An official of the Shri Amarnathji Shrine Board (SASB) that manages the affairs of the annual pilgrimage said, " A total of 1,612 pilgrims comprising 1,266 males and 346 females left Bhagwati Nagar Yatri Niwas today (Thursday) in 35 buses and 22 light motor vehicles in a convoy escorted by security forces for the Valley." "Since the Yatra started on July 2, two pilgrims have so far died of natural causes." An ice stalagmite structure inside the cave situated at 3,888 feet above the sea level wanes and waxes with the phases of the moon. Devotees believe the ice stalagmite structure called the 'Lingam' symbolises mythical powers of Lord Shiva. Pilgrims use the north Kashmir Baltal and the south Kashmir Nunwan (Pahalgam) base camps to reach the cave Shrine. From Baltal in Ganderbal district, pilgrims have to trek 14 km to reach the cave while those using the traditional Pahalgam route have to trek 46 km. The south Kashmir Pahalgam route passes through Chandanwari, Sheshnag, Pissu Top and Panchtarni. According to Hindu scriptures, this route that Lord Shiva used to reach the cave is where he told goddess Parvati the study of immortality and eternal life. Helicopter services are also available for the pilgrims from Baltal and Pahalgam to and fro the shrine. Due to heightened militant activities in the Valley this year, extra security measures have been taken to provide protection to the pilgrims. A three-tier security cover manned by the Army, Indo Tibetan Border Police Force, Central Reserve Police Force and state police are in place to secure the Jammu-Srinagar national highway which is the only surface link used by the pilgrims. The 48-day long Yatra will conclude on August 17 coinciding with Shravan Purnima and Raksha Bandhan festivals.