The alleged purchases relate to a host of items including snacks and books for children in institutions across the state.
Dubbing it as a "big scam", Congress and other opposition parties attacked the 8-month-old BJP-led government headed by Devendra Fadnavis.
Former chief minister and Congress leader Prithviraj Chavan demanded a CBI inquiry and said the scam exposed the "true colours" of the government.
Asked if he would demand Munde's resignation, Chavan said "Be it Pankaja Munde or Vinod Tawade (education minister caught in a row over educational qualification), this government would not remove anyone. After all, this the policy of the Modi government to brazen out all allegations."
The scam first came to light on June 15, when the office of Pankaja Munde received a letter from Ahmednagar Zila Parishad president Manjushree Gund complaining about the quality of chikki (a popular snack) distributed to tribal students under the Integrated Child Development Services (ICDS). Gund said the chikki was contaminated with clay.
This is the first time that an alleged scam of this magnitude has come to light after the BJP-Shiv Sena government took office.
All purchases were cleared by Munde, daughter of BJP stalwart late Gopinath Munde on a single day on February 13 through 24 Government Resolutions (GR).
Pankaja Munde was unavailable for comments. An official in her department said the minister was out of India and was expected to return on June 28.