(CBS News) DHAKA, Bangladesh -- When she was 11 years old, Tahmina Akhter Sadia went to work in a garment factory. Four years later, she's her family's breadwinner -- and a survivor of one of the worst industrial accidents in history.
"I didn't want to go into the factory that morning," she said, "because I'd already seen cracks in the walls. But the supervisor slapped my face and forced me to go inside."
Just before 9 a.m., Rana Plaza collapsed, burying workers in the rubble of an eight-story building.
Tahmina was trapped in a narrow space. She could see dead bodies around her and thought she would die herself. But after five hours, she was pulled to safety.
The supervisor who slapped Tahmina was killed.
She told us she still gets nightmares about what happened, as well as headaches and pain in her back.
"But I have to find another factory job," she said, "because we need to buy milk for my baby brother."
In the aftermath of the collapse, the Bangladeshi government has promised to improve factory safety. But labor groups say workers in the country are so powerless, they have no choice but to work in dangerous conditions.
We visited a factory that makes jeans for export. To give them a fashionable distressed look, workers spray them with toxic chemicals that can cause nerve damage. The workers don't wear face masks.
Other factories are adding extra floors, just as they did at Rana Plaza before it collapsed.
Watch: CBS News goes undercover in a Bangladesh clothing factory, below.
To film inside a precarious-looking factory, we had to use a hidden camera. The company makes children's clothing for European retailers, though many of the workers appeared to be children themselves.
And there was just one rickety fire escape for 400 people.
But standing up for the rights of Bangladesh's 4 million garment workers can be dangerous.
Hosne Ara Fahima is a widow at 33. Her husband, Aminul Islam, was a labor activist who angered factory bosses by encouraging workers to form unions and fight for better conditions.
Fahima told us the bosses retaliated by sending thugs to threaten and beat him up. Then, last year, Aminul disappeared.
His body was found two days later, dumped by the roadside. His kneecaps were smashed, and his toes had been broken. No suspect has been named.
Fahima told us she believes factory owners paid off corrupt police to torture and kill her husband.
"If you try to help workers in Bangladesh," she said, "you make enemies."
U.S. retailers have been trying to improve conditions in Bangladesh for many years, but there isn't any pressure on American companies to stop doing business in Bangladesh altogether.
Bangladeshi workers need these jobs, but a lot of people in Bangladesh told us that since U.S. retailers benefit from the country's very low wages, should take responsibility for conditions inside factories. Following the Rana Plaza collapse, several European retailers have signed an agreement to use their own money to make Bangladeshi factories safer, but so far, all of the big U.S. retailers have declined to sign on.