MILAN — Rome’s Colosseum is at the center of an investigation by Italy’s Court of Auditors.

The tax court has raised questions about the sponsorship contract signed in 2011 by the municipality of Rome and the Ministry of Cultural Heritage with luxury company Tod’s. The contract designates a sum of 25 million euros, or $35 million, for the restoration works.

In particular, the Court of Auditors has alleged that the sum to be paid by Tod’s might be too small compared to the advantages the company could reap from the sponsorship: Tod’s has control over the Colosseum’s image rights for 20 years.

In addition, the tax court pointed to a delay in the development of the restoration works, which might cause financial losses. While a relevant part of the works was completed last April, the construction of a service center and the restoration of the basement and corridors has still to be done.

“There was a delay in the works for Colosseum’s service center, but the tender notice will be done by the end of 2016, and the work will be completed within two years,” a Tod’s spokesperson said.

As reported last month, 31 of the iconic structure’s arches have been restored over a total surface area of 143,640 square feet. Some 109,620 square feet of travertine has been installed, as have new gates. A bas-relief of a gladiator and other architectural treasures have also been recovered.

Of the total amount Della Valle pledged, 10 million euros — or $11 million — has so far been spent. The restoration is expected to be completed in four or five years, between 2020 and 2022.

Tom’s has also established a foundation called “Amici del Colosseo [Friends of the Colosseum]” aimed at publicizing the restoration around the world and finding supporters to contribute to Italy’s artistic and cultural patrimony.