For the past decade Milan has been in the grip of an extraordinary property boom. Now, a sprawling corruption probe into the city’s real estate industry threatens to cast a shadow over Italy’s financial capital.

Prosecutors are investigating more than 70 people, including mayor Giuseppe Sala, while the city’s best-known developer will be questioned by the police and faces arrest, according to reports and documents seen by Bloomberg.

The investigation has sent shock waves through a city in the midst of a real estate renaissance. Once the core of Italy’s manufacturing sector, Milan’s inner-city industrial areas have been transformed to gleaming office blocks and high-end homes in recent years, with prices defying gravity and outshining the rest of the country where values have stalled.