The residents of the Al Azhar Housing Society near Safoora Goth had received death threats from unidentified persons one year back, a security source said.
For a few months, the Ismaili community was given proper security but after some time when everything remained peaceful the security was slowly withdrawn, the source added.
He said investigators have also found a pamphlet of the Islamic State at the site of the attack this morning proclaiming the advent of the terror group in Pakistan.
The attackers killed 45 people - 26 men and 17 women - and wounded more than 20 others before fleeing from the scene, police said.