EU competition regulators are seeking information from 400 companies to establish if there are problems in the market for voice assistants such as Alexa and Siri and other internet-connected devices that could lead to antitrust cases.
The European Commission has opened similar inquiries in the past into sectors such as e-commerce, pharmaceuticals, financial services and energy that led to cases against companies and eventually hefty fines.
Amazon's Alexa, Apple's Siri and Alphabet's Google Assistant are among the most popular voice assistant devices.
"It sends an important message to powerful operators in these market that we are watching them and that they need to do business in line with competition rules," European Competition Commission Margrethe Vestager told a news conference.
The EU executive said its interest was prompted by the large amounts of user data involved in consumer "internet of things" devices and it wanted to make sure market players did not use their control of such data to hurt competition or thwart rivals.
"Interoperability is of the essence if we want to make this market accessible," Vestager said.
Vestager, who can fine companies up to 10% of their global turnover for breaching EU antitrust rules, has made the tech industry the centrepiece of her enforcement efforts, taking on Google, Apple, Amazon and Facebook in recent years.
The European Union's antitrust chief Margrethe Vestager said on Thursday that EU court rulings this week, which saw courts reject a key EU tool used to transfer Europeans' personal data across the Atlantic and reject an EU order for Apple to pay 13 billion euros in Irish back taxes, were a "loss".
"The first thing you do when you get a court judgement is to read it very, very carefully. And we are still in the process of doing that. Of course, it's a loss, because it was an annulment by the court," Vestager said during an online event.
"The only comfort here is that the court agrees with us that we can use state aid tools to look at fiscal state aid as well. But now we read it very carefully, and then decide on next steps," she said.