The incident occurred this afternoon at the site of private construction company in Betavade village near Diva Agasan, Thane police Public Relations Officer Gajanan Kadbule said.
A worker executed the blast but failed to alert his co-workers, police said.
The mine blast was being carried by the construction firm since the past two months as a part of the digging work to lay the foundations (for the building), he added.
The injured have been admitted to private hospitals and a case under relevant sections of IPC was registered, police said, adding investigations were underway.