Naib Subedar Patan Kumar Poddar, posted at EME Unit at Secunderabad, allegedly gave the woman - who had befriended him on social media - classified information about deployment of Army units, location of Artillery regiments, etc.
Poddar (41), belonging to Malda of West Bengal, had joined Army as a clerk in August 1996.
The police's remand report said that he came in contact with a woman, who identified herself as Anuskha Agarwal, on Facebook in 2013.
Initially she asked him to work for the NGO through online surveys, and later started seeking classified military information, including photographs of missile unit and storage unit, their movement, etc.
Meanwhile, a senior officer supervising the probe said police were going seek details of accounts of Poddar and the woman from Facebook.
Police have sought a seven-day custody of Poddar. The matter is likely to come up for arguments tomorrow. Poddar is presently under judicial custody.