The incident took place under Dhanpuri police station area.
Siyabai (35) and her nephew Tula Kushwaha (20) were killed when the mud mound collapsed on them while ther were engaged in digging, Dhanpur Police Station Inspector Satish Dwivedi said.
The duo died instantly, he said, adding their bodies were sent for post-mortem.
Dwivedi said a case has been registered and further investigation was on.