RABAT, Morocco—Heavy rains flooded an illegal garment factory in the northern Moroccan city of Tangier, killing at least 28 workers Monday, state television quoted a medical official as saying. That raised the death toll from 24, reported earlier by the Moroccan news agency MAP. Local authorities said firefighters and emergency workers rescued 10 people from the factory, in the basement of a residential villa. Rescuers searched for others who might have been trapped in the sudden flooding. The total number of laborers at the site wasn’t immediately known. An investigation was opened. A shaken unidentified woman who emerged from the flooded basement told TanjaNews, a local site, that no one was prepared for the deadly deluge. “There was nothing to worry about. We were working as usual,” the woman said. “And then because it was raining, as you can see … the water started entering, a little water, even my …