The owner of the building had been warned in advance of an impending Israeli missile strike, the source reported, and the building had been evacuated.The Israeli military did not immediately provide comment on the incident.
The building also contained a number of apartments and other offices.
In Gaza, at least 139 people have been killed since Monday, including 39 children and 22 women. In Israel, eight people have been killed, including a 5-year-old boy and a soldier.
Early Saturday, an Israeli airstrike hit a three-story house in Gaza City’s Shati refugee camp, killing eight children and two women from an extended family.