On April 24, two days before the bombing, Habitan and Bukhsh left the city and went to Balochistan, according to the officials.

One of them recalled that the man Hayat later married, Habitan Baloch, was a leading figure in BSO Azad at the time.

On the day of the Karachi attack, Habitan, a dentist, tweeted that he was "beaming with pride" at what his wife had done.

The post has since been removed and Pakistani authorities say they do not know the whereabouts of Habitan or the couple's children.

When the facility proved inaccessible, Bukhsh was invited by a BLA operative to meet Habitan, who communicated to him that the new target was to be Chinese teachers at Karachi University, the sources involved in the probe said.