The outages were not caused by an outside attack, the person said, declining to be named because the discussion concerned internal Yahoo matters.
Microsoft’s Bing search engine powers Yahoo search under a 10-year deal announced in 2009. Yahoo was not immediately available for comment. Microsoft confirmed the outage, but declined to comment on the cause.
On Friday afternoon, users who typed search.yahoo.com got an error message saying that Yahoo engineers were working to resolve the issue. The search engine appeared to be working again later in the day.
After the crash, Microsoft’s roll-back procedure failed, forcing it to shut down its groups of linked servers to get back the point where everything worked smoothly, the person said.
Once the problem was resolved, Yahoo had trouble handling the backlog of search requests, the person added.
“This morning, some of our customers experienced a brief, isolated services interruption which has now been resolved,” a Microsoft spokesman said in a brief statement Friday.