Dexter Area Fire Chief Loren Yates said the victims were working on the tank at the Dexter Utilities Department when the blast occurred, AnnArbor.com reported.
Yates said firefighters believe both men were inside the tank attempting to disassemble it when methane gas exploded.
The force of the explosion blew one of the victims to the roof of a nearby building.
Justin Bieber crashes Drake Bell's album release party
Rosie O'Donnell unveils nearly 50-pound weight loss