Google has faced some European Union antitrust scrutiny as of late, but the company's troubles might have only just begun.

The Financial Times reported Thursday, citing EU documents it claims to have seen, that the governing body's competition watchdogs are conducting an informal investigation into whether Google is violating competition regulations with its Android operating system. According to the documents, Microsoft and Nokia, among other competitors, have complained to the EU that Google is violating competitive rules with its handling of Android.

The Financial Times story follows a report from The New York Times in April, saying that the EU competition chief Joaquin Almunia was quietly investigating Android after FairSearch Europe, a group of companies that includes Microsoft, Nokia, and Oracle, filed a complaint against Google for allegedly using Android as a "deceptive way to build advantages for key Google apps in 70 percent of the smartphones shipped today."

It appears that the Financial Times' report covers the same ground. However, the documents the site has discovered also include mention of a 23-page questionnaire that the EU competition regulators have sent to device makers and carriers, asking for them to chime in on whether Google is acting unfairly with Android.

According to the documents, the competitors are concerned that Google is offering Android "below cost" to boost support for its operating system. They also argue that Google has the power to force device makers to "cancel and/or delay the launch of smartphone devices" that aren't running Android.

The "below cost" argument might be a tough one for competitors to win on. Google offers the open-source Android for free. What device makers want to do with the platform after that is entirely up to them. That has been a key component in the company's success to this point.

Still, the EU is doing its due diligence and will likely evaluate the answers to its questionnaire. Whether the informal investigation will ever go beyond that stage, however, remains to be seen. At this point, neither Google nor Android have been formally charged with any violations, and likely wouldn't be hit with such charges for quite some time, if they ever come to fruition.

"Android is an open platform that fosters competition," Google told CNET in an e-mailed statement. "Handset makers, carriers and consumers can decide how to use Android, including which applications they want to use."

Updated at 6:13 a.m. PT to include Google's statement.