"The issue with Google Ad Manager has been resolved and ad serving has now been restored for the affected users,” Google said in a tweet on Thursday evening.
“We apologize for the inconvenience.”News websites such as the New York Times, Washington Post, Wall Street Journal and Los Angeles Times were being affected by the issue, one of the sources said.
The New York Times, Washington Post, Wall Street Journal and Los Angeles Times and Google did not immediately respond to requests for comment.
Ad Manager has about 90% share of the U.S. market for ad-serving software, which publishers embed on their websites, according to an ongoing antitrust lawsuit Texas and other states have been pursuing against the tech giant.
The lack of competition has left publishers with few back-up options to Google Ad Manager, the sources said, and lawmakers in the U.S. and elsewhere are pursuing legislation to curb Google's market power.