Investigators probing the death of five men at a scrapyard said CCTV showed an "apparent shift in a wall's angle seconds before it collapsed", an inquest has been told.
The workers died instantly from a "catastrophic failure" of the concrete partition at Hawkeswood Metal Recycling in Birmingham in July 2016.
Part of a stored pile of 263 tonnes of metal ingots in an adjacent bay backing on to the wall also fell on the men.
A jury inquest will last for two weeks.
Alimamo Jammeh, 45, Ousmane Diaby, 39, Bangally Dukureh, 55, Saibo Sillah, 42, and Muhamadou Jagana, 49, were clearing out a scrap metal storage bay when they were killed at the Nechells plant.
The victims suffered "devastating blunt force injuries" and had to be identified by their fingerprints, a hearing in Birmingham was told.
Paul Cooper, a Health and Safety Executive (HSE) expert, told the inquest that West Midlands Police had analysed CCTV footage of the collapse and their report stated a shift in the wall's angle before it crumbled.
He said the total amount of metal collected from an adjacent bay to where the wall collapsed was "the equivalent of five full articulated lorries."
But the exact amount of fallen metal debris from one bay to another has not yet been revealed.
Site supervisor Jordan Mahoney told the inquest he heard "screaming in front of him about 10 to 15 steps away."
He radioed for help before he got out and a manager and other staff were there "within seconds."
Mr Mahoney, who helped build the concrete wall, told the hearing he did not know if there was an inspection system for the walls and did not know who was in charge of health and safety at the site.
He said there was no discussion on the function of the wall and he never saw a written safety document on how to build the walls and did not know who decided on using the blocks.
Survivor Tombong Conteh told how his leg was pinned under rubble when it came crashing down.
Speaking through a translator, Mr Conteh, who had been working at the site for two months, said: "My leg was stuck under the rubble. I did not know what was going on.
"I can't tell you anything about who extracted me. I can't remember."
The labourer, who limped into the dock to give evidence, said he was not working due to injury.
During the first day of the inquest on Wednesday the widow of Mr Jammeh said she had still not told her children of the tragedy.
Jurors heard all five men - four from The Gambia and one from Senegal - had been working in Spain before moving to the UK for better job prospects.