Two other labourers were injured when the incident occurred in the field in Sultanpur Patti in Bajpur in Kosi river area of the district yesterday, a senior police official said.
Layers of earth were removed with great difficulty by other workmen to pull out the labourers, Additional Superintendent of Police, Kashipur, Jagdish Chandra said.
"While three of them died on way to the hospital, two labourers who suffered serious injuries are still battling for their lives at a hospital in Kashipur," the ASP said, adding A father-daughter duo among those killed in the incident.