Prosecutors in January dismissed animal cruelty charges against Green Acre Dog Boarding owners Jesse Todd Hughes, 32, and Maleisa Maurine Hughes, 45, of Gilbert.
Maricopa County Attorney Bill Montgomery said at the time that the case presented to a grand jury didn't take into account the potential for problems with an air conditioning unit for the room where the dogs were kept overnight.
A subsequent review indicated there is enough evidence to support the charges, Montgomery said Wednesday as he announced the latest 29-count indictment.
As in the original indictment, the Hugheses also face a fraud charge accusing them of making false promises to the dogs' owners.
The allegations did not extend to Logan and Austin Flake, who were caring for the dogs while the Hugheses were on vacation. The Flakes discovered the animals and were previously accused of animal cruelty.
Austin Flake is a son of U.S. Sen. Jeff Flake, R-Ariz. But Montgomery said Austin Flake's family ties had no bearing on whether he and his wife would be charged.
The Hugheses face a June 3 arraignment on the new indictment.
"Just as before, there is no evidence of criminal conduct," said Robert Jarvis, a lawyer for the Hugheses. "It was a tragic and freak accident. The evidence has not changed. There was a lack of evidentiary support for the charges before, and there remains a lack of evidence now."
As the business's owners, the Hugheses directed the caretakers on what to do and were chiefly responsible for the conditions in which the dogs were kept, Montgomery said.
An initial theory in the dogs' deaths was that the room's air conditioning failed because a dog chewed through a wire. However, further investigation indicated the air conditioning unit itself had failed, authorities said.
Absent that failure and the large number of dogs placed in the room, "I don't know if we'd be here today," Montgomery said.
The animal cruelty charges include felonies and misdemeanours. Some accuse the Hugheses of subjecting the dogs to "cruel neglect or abandonment that resulted in a serious physical injury." Other say the couple failed to provide necessary medical attention.
Maricopa County sheriff's investigators in September recommended 21 felony charges of animal cruelty and various misdemeanours against the Hugheses and the Flakes.
"I understand that the objective of the county attorney's office is to secure a conviction," Sheriff Joe Arpaio said in a statement Wednesday.