Gap has said it was “terribly saddened” by the deaths of workers at a Bangladeshi factory razed to the ground by a fire this week, and that it would investigate the cause of the blaze.

Some 31 workers were killed and 200 more injured in the fire on Tuesday which swept through the Hameem plant in the Ashulia district near the capital Dakha.

The Bangladeshi factory will reopen on Saturday according to reports.

Gap dispatched a team to the site of the fire and said in a statement that it was “terribly saddened” by the deaths.

The US giant added: “We will work with the other companies that utilise this facility as well as our industry partners to ensure we understand what occurred, and that the workers and families are supported.”

Labour rights groups, including the Clean Clothes Campaign in Europe and the Maquila Solidarity Network in North America, said that the latest fire in the country, which is favoured by retailers as a manufacturing base because of the low cost of labour, highlighted their safety concerns.

They called for improved fire safety inspections and strengthening worker representation.

The Clean Clothes Campaign, a clothing workers’ safety watchdog  in 15 European countries, alleged that Hameem was known for “unauthorised subcontracting, meaning the factory may have also been producing for brands which are unaware of their production there.”

Gap’s code of conduct for suppliers requires them to obey local fire regulations, and have “sufficient, clearly marked exits, allowing for the orderly evacuation of workers in case of fire or other emergencies”.

It also requires fire extinguishers, clearly marked and unobstructed emergency exit routes, and regular evacuation drills.

Gap also ensures that all the factories it uses are inspected regularly by independent auditors.

Hameem says on its website that it supplies leading US and European retailers including Gap, H&M, Target and Walmart.