A federal investigator is expected to visit Honolulu next month as part of a developing grand jury probe into the Honolulu Authority for Rapid Transportation, the agency charged with building the city's rail project.

The investigation came to light last week when HART acknowledged it had received a federal subpoena asking for thousands of documents on the construction of the city's $9.2 billion rail system, the largest capital improvement project in the state's history.

The transit agency said it was informed of a second subpoena, one calling for information about the real estate services required to acquire and relocate homes and businesses to build the rail system.

The agency said in a statement that HART reported to the Federal Transit Administration that it "may have overspent on relocating residences and businesses in the path of the rail line."

Andrew Robbins, HART executive director and CEO, told reporters at a press conference Thursday that the overpayments may have amounted to about $4 million.

"But what we did last year was we offset the federal reimbursement. Essentially paid the federal government back, and used local funds instead. So that it would not be an issue with the federal government – in terms of payments," he said.

The second grand jury subpoena dated Feb. 3 seeks records involving the "Overland, Pacific, and Cutler (OPC) Internal Relocation File Audit Report" prepared in December for HART. The subpoena also seeks HART's Real Estate Acquisition Management Plan and documents relating to 18 relocations files, including the appraisals, offers made to landowners, settlements and records on relocation assistance.

In a statement today to the HART Board of Directors, the agency said it is reporting the issue on relocation funding to the FTA and the Federal Department of Transportation Inspector General.

While talking with reporters, Robbins said HART wants to demonstrate to the FTA that they "have taken a number of corrective actions to make sure that situation doesn't happen again."