"We ran to the door. It was blocked, to the elevator, it was blocked. Then ... the lights went out," Rachida Darif told The Associated Press.
Darif said she saved herself by crawling through a space to the roof, then jumping down from a neighboring building that was under construction. She said she used a construction cord to lower herself part way and then jumped.
The Wilaya of Greater Casablanca, the city government, said in a statement that 55 were killed and 12 were injured, MAP reported.
About 100 people were in the factory when the fire broke out at about 10 a.m. and quickly spread through the four-story building, according to MAP. Chemical products in the factory added to the fury of the flames, the official statement said.
However, the exact cause of the blaze was not immediately known. Officials from the prosecutor's office opened an investigation into the fire, MAP said.
The fire was the worst reported in Morocco in recent years. A 2002 fire at the overcrowded Sidi Moussa prison, in the Atlantic coastal town of El Jadida, killed 50 people. That fire was caused by a short circuit but made more deadly by fumes from burning mattresses.
The bustling coastal city of Casablanca is Morocco's leading port and the economic capital of this North African country. It reflects the contrasts of Morocco, the westernmost Muslim country, with its rich modernity and poor, crowded neighborhoods with soaring unemployment.