An airstrike on a three-story home last summer killed the wife and two children of Mohammed Deif, but the fate of the elusive Deif, who has survived several Israeli assassination attempts, was not known.
The Israeli officials say they believe Deif was in the building shortly before the airstrike. They say it is not clear whether he was there at the time of the attack, but now believe he is alive.
The officials spoke on condition of anonymity because they were discussing a classified assessment.