ANI reported the sources as saying NTRO (National Technical Research Organisation — a technical intelligence agency which comes under the National Security Adviser) surveillance confirmed the presence of 300 active mobile phone connections at the camp.
The sources added that other intelligence agencies had reported the same findings.
ANI did not say who the sources were.
Sources: NTRO surveillance of JeM Balakot camp in days leading up to air strike by IAF confirmed around 300 active mobile connections in facility pic.twitter.com/uwyzd0qpHB
India struck the JeM camp in Pakistan's Khyber Pakhtunkhwa province after the February 14 attack on a Central Reserve Police Force convoy in Pulwama, Kashmir in which at least 40 CRPF personnel were killed. The Pulwama attack was claimed by the JeM.
The number of casualties from India's air strike been the biggest sticking point ever since the strike.
After the strike, news reports appearing in the Indian media had said the number of casualties could be as high as 350.
Pakistan has said there were none.
On Sunday, BJP President Amit Shah said 250 cadres of the JeM were killed in the strike.
The sources said the number of cellphone connections were confirmed by the National Technical Research Organisation — a technical intelligence agency under the National Security Adviser — and other intelligence agencies.