Kumar's transfer to the Environment Department as secretary comes days after a row over the state's COVID-19 data, said official sources.
Nigam, who was the Transport Secretary, has beenappointed as Kumar's replacement, as per a notification dated May 11.
West Bengal has so far reported 118 deaths due to coronavirus infection.
The state has attributed 72 other deaths to comorbidities -- cases where COVID-19 was incidental.
The state has reported 1,939 COVID-19 cases till Monday and of them, 1,374 are active. SCH SOM DVDV