Emergency services said they were working when a 15ft (4.5m) concrete bay wall collapsed on them at 8.40am.

Blocks weighing about one-and-a-half tons each came down, along with tons of scrap metal being stored in an outside yard.

All five men were pronounced dead at the scene following the incident, at the Hawkeswood Metal Recycling in the Nechells area.

Three of the victims have been named locally as Saibo Saillah, aged 42, Alimamo Jammeh and Bangaly Dukureh, who were both from Aston in Birmingham. All three were married with young families.

A sixth man is currently in hospital after suffering a leg injury, which is not thought to be life-threatening.

Friends and relatives of the men, who were at the scene awaiting more information, said they were all Spanish but of Gambian origin.

Detective Superintendent Mark Payne, of West Midlands Police, said a joint Health and Safety Executive (HSE) and police investigation had been launched to establish the cause.

He added that one line of of inquiry would be to find out whether "any issues of negligence or malpractice" may have contributed to the collapse.

Mr Payne said: "We're simply trying to recover the bodies of the men and do it in a way which will help understand exactly how that wall came to fall down.

"Clearly we are investigating together with the HSE, whether there are any issues of negligence or malpractice that have contributed to that wall falling down."

Emergency services said they have accounted for all staff who were on site and that there was no prospect of anyone having survived under the many tons of rubble.

There was a major blaze at the site in February - but Mr Payne said there was no evidence to suggest that fire damage had caused the wall to collapse.

'Devastating'

Shabana Mahmood, Labour MP for Birmingham Ladywood, described the accident as "devastating news" - and warned there would be serious questions to answer.

She said: "Nothing will bring their loved ones back but the families of those who have been killed will want answers, they will want to understand what has happened here.

"I am extremely shocked that five lives have been cut short so abruptly like this."

The Prime Minister has also offered his condolences to the victims' families, and said he was "shocked to hear about the tragedy in Birmingham".

Hawkeswood Metal began trading more than 40 years ago. According to the company's website, it processes more than 500,000 tonnes of scrap metal a year.

In July 2012, it was fined £50,000 and ordered to pay more than £10,000 in costs at Birmingham Crown Court after a worker trapped and broke his arm in an unguarded conveyor belt, documents from the HSE show.