Twelve labourers were working at the construction site on VIP road here when suddenly the parapet of a wall along with sand fell on them, an official from III-town police station said.
The four labourers got buried under the debris and died of suffocation, he said.
The other labourers were unhurt.
Three bodies were extricated from the debris while efforts were on to retrieve the body of another labourer.
The deceased were yet to be identified, the police officer added.