Google is shutting down its much-maligned social network, Google+, after user data was exposed.
It said a bug in its software meant information that people believed was private had been accessible by third parties.
Google said up to 500,000 users had been affected.
According to a report in the Wall Street Journal, the company knew about the issue in March but did not disclose it.
The WSJ quoted an internal Google memo that said doing so would draw “immediate regulatory interest”.
A spokeswoman for Google said that whenever user data may have been affected it determines whether to tell people based on a number of criteria.
“Our Privacy and Data Protection Office reviewed this issue, looking at the type of data involved, whether we could accurately identify the users to inform, whether there was any evidence of misuse, and whether there were any actions a developer or user could take in response.
“None of these thresholds were met here.,” she said.
Google+ was launched in 2011, quickly becoming a failed attempt to compete with Facebook.
Speaking about the exposed data, Google said on Monday: “We found no evidence that any developer was aware of this bug, or abusing the API, and we found no evidence that any profile data was misused.”
Google said it would continue to offer private Google+-powered networks for businesses currently using the software.