Lokayukta N K Mehrotra also served notices to two other state mining department officials, an official of Lokayukta office said.
"Notices were served yesterday to Principal Secretary (Mining) and Director (Geology and Mining), who have been asked to appear before Lokayukta on January 9 and 12 respectively", the official said.
He also said that Lokayukta also gave notices to Prajapati's wife Maharaji and sons Anil and Anurag asking them to file their reply by January 8 in connection with acquisition of various immovable properties by them.
A complaint was filed with Mehrotra by Om Shankar Dwivedi on December 11 against the minister alleging that he has amassed wealth disproportionate to his known sources of income.
The Lokayukta had said he would probe the matter on the basis of "whatever" documents he has before him.
It was also alleged in the complaint that Prajapati's relatives including wife, sons and daughter Ankita have bought immovable properties at the cost of Rs 340.49 crore and their current market value is over Rs 1,000 crore.
Prajapati has denied allegations against him and has offered to quit politics, if charges against him were found true.