European Union regulators said Monday they were investigating whether software giant Microsoft Corp. used its market dominance to squeeze...

BRUSSELS, Belgium — European Union regulators said Monday they were investigating whether software giant Microsoft Corp. used its market dominance to squeeze out office software and Internet browser rivals.

The European Commission said it is opening two formal probes against the company. A court last year backed the EU in a long-running legal battle over Microsoft’s actions in using its ubiquitous Windows operating system to elbow into new software markets.

The EU will examine whether Microsoft withheld information from companies that wanted to make products compatible with its software — including Office word processing and spreadsheet programs, some server products and Microsoft’s push into the Internet, the .NET framework.

The EU said it will also look at whether Microsoft’s format for archived documents — Office Open XML — “is sufficiently interoperable with competitors’ products.”

The second probe — triggered by a complaint from Norway’s Opera browser — will look at whether Microsoft illegally packages its Internet Explorer browser with Windows, checking if “new proprietary technologies” harm competition by reducing compatibility with open Internet standards.