California ? Computer users doing Google searches during a nearly one-hour period Saturday morning were greeted with disturbing but erroneous messages that every site turned up in the results might be harmful.

The company blamed the mistake on human error and apologized for any inconvenience caused to users and site owners whose pages were incorrectly labeled.

The glitch occurred between 8:30 a.m. CST and 9:25 a.m. CST, Google Inc. said in an explanation on its company blog. Anyone who did a Google search during that time likely saw the message “This site may harm your computer” accompanying every search result, the company said.

Google said it routinely flags any search results with that message if the site is known to install malicious software in the background or otherwise surreptitiously, a practice aimed at protecting its users.