"The workers were operating from a timber platform supported by a scaffold made of old wooden planks and due to the weather element the structure had become weak and unsound hence could no longer support the weight of the workers, equipment and materials," he said.
At the same time, Arumonyang urged constructors and personnel working on construction sites to work on platforms and scaffolds that are strong enough to sustain the weight.
He challenged the contractors to also provide healthy and safe working conditions for the workers and ensure their works are approved by state regulators.
"A multi-agency inspection and assessment of the site will be conducted forthwith and action taken on any parties found culpable in the witnessed casualties," Arumonyang added.
The PS acknowledged the rescue team led by the Kenya Red Cross Society (KRCS), police and emergency response units from the national disaster management unit for their swift action during the Eastleigh incident.
The scaffolds of the building identified as Kuja B Estate on Muratina Road collapsed when the workers on site. The injured were evacuated to Kenyatta Hospital and other medical facilities.
"Kuja B Estate building scaffolds collapse. A multi-agency search and rescue operation is ongoing. Fifteen casualties have been evacuated to Kenyatta Hspital and other facilities. Four fatalities were reported. KRCS Nairobi to set up a PSS and Tracing desk. More updates to follow," Kenya Red Cross said.