In 1998, I was studying anthropology in Paris, but went home to Tangier for the summer. I’d been given an assignment on food so when a friend mentioned she had a job in a prawn processing factory, I decided to go along and take some shots.

It was a Dutch plant on Moroccan soil, an early example of globalisation. The prawns were fished from the North Sea and brought to Tangier to be peeled. I was told women were preferable as employees because they had less union representation.

I got a tour and took as many pictures as I could, mostly in black and white. I had a few colour rolls in my bag so, towards the end, did some shots with them. This was taken from the changing room upstairs, behind a glass window. The women wore blue hairnets and had numbers on their blouses. The blue light on the ceiling was to kill mosquitoes and that big tube running down the centre pumped in cold air – the sound was deafening.

There were bits of prawn everywhere. The women would peel all day. They’d peel and peel and peel, dropping bits every now and again, then run to the back to have their baskets weighed, before running back to their places. Since they’re paid by weight, they work very quickly but they’re so skilled they can chit-chat as they go. A floor manager – you can see her on the left – walks up and down, telling them to be quiet and get back to work.

Just being there made me tense. I kept waiting for someone to ask: 'What are you doing?'

I was fascinated by these quasi-medieval labour conditions. It was a non-stop factory. Women are bussed in and out and locked up all day, only allowed very short breaks out front. There’s no common room with a library, no day care, no place to sit down and eat together. Just being there made me feel tense. I kept waiting for someone to ask: “What are you doing?” Although I had permission, it wasn’t entirely above board.

About 10 years after I took this, a friend of mine, Leïla Kilani, made a film called Sur la Planche – about exactly this kind of processing plant. The footage taken inside the factory was just like my photos. Kilani was obviously struck by the same thing I was. There’s a beautiful scene where the main character – a young woman who works in the cold room – has a bath to get rid of the smell. She’s determined to do whatever she can to get out of the plant and she washes herself furiously, removing the humiliation of her lowly worker’s status. It’s a beautiful moment of emancipation.

The prawn plant was in the first free-trade zone in Tangier. Now there are many more and the conditions are no better. The industries have changed, though. We make a lot of cars now and whole areas have been built to house the migrant workforce – huge white buildings all around the city. I have now taken pictures in a yoghurt plant, as well as toilet and ceramic factories.

I’m currently building a public garden in Tangier, filled with all the plants used for dyes throughout history. Right now I’m working with cochineal, the insects used to make carmine. It really stinks, much like the hands of the factory workers. So I’ve come full circle.

• Yto Barrada’s solo show Agadir is at the Barbican, London, until 20 May.

Yto Barrada’s CV

Yto Barrada. Photograph: Benoît Peverelli

Born: Paris, 1971.

Training: Political science and history at the Sorbonne in Paris; seminar at the Paris Ecole des Beaux-Arts; photography at the International Centre of Photography

Influences: “Maya Deren, David Hammons, Raoul Hausmann.”

High point: “In the darkroom making photograms with candy wrappers.”

Low point: “Losing negatives.”

Top tip: “Dig around in your relatives’ drawers for old negatives to make a book online.”

