The owner of the eight-storey factory complex which collapsed in Bangladesh last week killing at least 377 people has been arrested.

Mohammed Sohel Rana, who had not been seen since Wednesday’s collapse of the building which supplied clothing to multinational retailers including Primark and Mango, was flown back to the capital Dhaka by police helicopter from the country’s border. His wife had already been arrested.

Rana had approval to construct five floors but added three more floors illegally, it has been reported.

A further nine survivors were found yesterday, in addition to the 29 rescued alive on Saturday. However a fire broke out as rescuers tried to cut through steel yesterday injuring three people and killing one, the AFP agency reported.

The building housed five clothing factories employing 3,122 staff. It is not known how many people were in the building when it collapsed however 2,500 people have been accounted for.

Police have arrested three factory bosses – Mahmudur Rahman Tapash, chairman of New Wave Apparels, its managing director Bazlus Samad and Aminul Islam, chairman of Phantom Apparels – as well as two engineers who approved the building’s design.

Campaign group War on Want targeted Primark’s store at the west end of Oxford Street on Saturday carrying placards. They have called for the retailer to sign the Bangladesh Fire and Building Safety Agreement to end the “appallingly unsafe factory conditions” in the Asian nation.

Primark said last week it is seeking an agreed methodology for testing the integrity of buildings where there are multiple factories on multiple floors with different tenants. “It is not easy to agree how this will be achieved, but this is what the company is seeking and it will ask the ETI [Ethical Trading Initiative] to look into this issue,” a Primark spokesman said.