The factory employs about 6,000 people in Gazipur near Dhaka.
Habibullah said the sick workers suffered from vomiting and nausea starting about two hours into their shifts Wednesday. They were given mainly saline at hospitals and those who were improving left by Thursday.
The factory was shut down Wednesday.
A building collapse near Dhaka last month killed 1,129 workers, injured others and highlighted the hazardous working conditions in thousands of garment factories in Bangladesh.