An engineer who warned a factory in Bangladesh was unsafe the day before it collapsed has been arrested.

The death toll in the country's worst industrial tragedy has now passed 500, with many more workers still missing.

Adbur Razzak is the ninth person to be questioned by police following the accident nine days ago.

 

The eight-storey Rana Plaza in Dhaka housed five clothing factories, including one which made garments for Primark, the retailer which operates as Pennys in Ireland. 

Khan was a consultant for Mohammed Sohel Rana, the building's owner, when three floors were illegally added.

He was called to inspect the building when it developed cracks on April 23 and later appeared on television, saying he had told Rana to evacuate workers because the structure was not safe.

Police ordered an evacuation but witnesses say Rana told people gathered outside the building on the morning of the tragedy that it was safe to go inside.

Hours later, the complex collapsed into 600 tons of rubble with around 3,000 people inside.

Lieutenant Mir Rabbi, of the Bangladeshi army control room, said the death toll now stands at 501.

More than 100 people are still missing.

Rana has also been arrested and is expected to be charged with negligence, illegal construction and forcing workers to join work.

The offences are punishable by a maximum of seven years in jail.

Bangladesh's prime minister has defended the country's response to a deadly building collapse.