WASHINGTON (AFP) - The search engine Google sparked online confusion Saturday when a glitch in its security program temporarily warned users that websites from all search results were potentially harmful. Between 1430 and 1525 GMT, sites turned up in search results were marked as harmful and users received the message: "Warning This site may harm your computer." "What happened? Very simply, human error," Goggle vice president for search products and user experience Marissa Mayer said on the company's official blog. Google receives regular updates to a list of malicious websites from StopBadware.org, which investigates consumer complaints. "We periodically receive updates to that list and received one such update to release on the site this morning," Mayer explained. "Unfortunately (and here's the human error), the URL of '/' was mistakenly checked in as a value to the file and '/' expands to all URLs." Users who tried to access the site were blocked by Google, which directed them to StopBadware.org. The firm works with Google to determine which sites are dangerous. "This led to a denial of service of our website as millions of Google users attempted to visit our site for more information," StopBadware.org said in a statement. Google was back to normal between 1510 and 1525 GMT. The company expressed "apologies to any of you who were inconvenienced this morning, and to site owners whose pages were incorrectly labelled." The Mountain View, California-based company said it "will carefully investigate this incident and put more robust file checks in place to prevent it from happening again." The outage, widely discussed on Internet blogs and forums, did not affect Google's news search service. Google controls about 70 percent of Internet searches, a market share that has grown steadily in recent years.