The city Department of Investigation is probing the Bloomberg administration’s bungled $2 billion overhaul of the 911 emergency-call system for evidence of corruption, fraud and violations of city regulations, The Post has learned.

Agents have focused on the money trail — such as cost overruns, contract payments and other expenditures — connected with the Emergency Communications Transformation Project, which actually made the system worse than it was before.

“It’s looking at it comprehensively,” a source told The Post.

The inquiry is preliminary, and probers have not found any proof of criminal conduct, sources said.

But the DOI will open a full-blown criminal case “if the review finds possible corruption,” a source said.

The investigation has been going on for months, even as Hizzoner, in public appearances, continues calling the project a success.

Mayoral spokesman Marc LaVorgna declined to comment.

The inquiry is similar to the probe that led the DOI to uncover more than $600 million in fraud and kickbacks connected with the CityTime payroll system. That case became the biggest scandal in the Bloomberg administration.