It spent €200m to buy the property and convert it into a datacentre, and a further €150m on a subsequent project to restore its machine hall, which is due for completion early next year.
The latest round of investment, announced on Monday will be used to increase the datacentre's size threefold, according to Google. The company attributed the expansion due to growing demand from consumers for mobile video, Bloomberg said.
Headcount at the facility will rise from 90 to 125 as a result of the expansion.
Facebook also has a large datacentre in the region, although its facility is located in neighbouring Sweden. Based in Luleå, near the Arctic Circle, the datacentre is Facebook's first outside of the US, and went live in June this year.