The wall collapsed when the labourers resumed their work after a brief break owing to heavy rain, they said.
Following the incident, locals rushed to the spot and started rescue operation but three of the labourers died on the spot, police said.
Basanti Devi (44), Jahangir Nadas (50) and his 25-year-old son Shamsad Nadas, hailing from Purnia in Bihar, died on the spot while Sageer succumbed to the injuries during treatment, they said.
Chand Mohammad, who was injured in the incident, is undergoing treatment, police said.
More From This Section
According to police, Banwari Lal is absconding.
In a separate incident, 48-year-old Madan Singh today drowned in Yamuna river at Bengali Ghat here while performing rituals, police said.
Efforts to rescue him failed and later divers fished out his body.