They include the brother and another relative of Masood Azhar, the founder of the group that claimed the attack.
Pakistan, which has been under international pressure to crack down on militancy, said 44 suspected militants are in “preventative detention”.
Many feared the escalation of tensions could trigger a dangerous conflict.
How did the latest tensions unfold?
It began on 14 February when a suicide bomber killed more than 40 Indian soldiers in Indian-administered Kashmir.
Jaish-e-Mohammad (JeM) said it carried out the attack – the deadliest to take place during a three-decade insurgency against Indian rule in Kashmir.
On 26 February, India retaliated by carrying out air strikes on what it said was a JeM militant camp in Pakistan.
Pakistan – which denies any involvement in the 14 February attack – said it had no choice but to respond and the day after the strike, a dogfight between the sides led to an Indian fighter jet being shot down in Pakistan-administered Kashmir.
The fighter pilot, who was captured by Pakistan, was released on 1 March and arrived in India, where he has been hailed as a hero. The countries have retreated from the brink of further confrontation since then, but angry rhetoric has persisted.
Indian politicians have hailed their strikes as successful and Prime Minister Narendra Modi has given rousing speeches at rallies, positioning himself as the protector of the country’s borders.
But new satellite images have raised questions over India’s claim to have demolished JeM training camps in Pakistan.
Images released by US firm Planet Labs appear to show a religious school run by JeM to be standing – even after the strike. Whether or not it is in fact linked to the militants cannot be independently verified, but the images show the site that India said it hit.
What does Pakistan’s latest move mean?
Addressing the militant detentions, Pakistan’s Interior Secretary Azam Suleman Khan told the BBC that if investigators find “evidence against them, they will be proceeded against,” and if not they will be set free.
JeM is designated a terror organisation by India and the UN, as well as the UK and the US.
At least some of those held are thought to be named in an Indian dossier handed to the Pakistani authorities investigating last month’s attack.
Analysts are also sceptical over whether these arrests will be an effective measure, as they were not accompanied by any investigation or signs of a serious crackdown on suspected militants.
Some critics suggest the move is a symbolic gesture meant to defuse mounting international pressure. In the past suspected militants have circumvented attempts to rein them in.
India accuses Pakistan of allowing militant groups to operate on its territory and says Pakistani security agencies played a role in the Kashmir attack -these are allegations Pakistan has consistently denied.
