NEW YORK (CNN/Money) - The investigation into the leak of Microsoft Corp.'s source code has turned to a small software developer that has had access to the code since 1994, according to a published report Tuesday.

San Jose, Calif.-based Mainsoft Corp. said late last week it is cooperating with Microsoft and law enforcement officials after reports that some of the leaked code came from its computers, the Wall Street Journal reported.

"This may be the impetus for Microsoft (MSFT: Research, Estimates) to seriously take a second glance at how they protect their source code," Scott Marrs, an attorney for Beirne, Maynard & Parsons LLP, told the paper.

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Microsoft makes its source code, or the blueprints to its software, available to about 3,000 entities, including customers and governments, the newspaper reported.

Access to the code may allow hackers to more easily break into Windows-based computers or write viruses that exploit flaws in the software programs.