BEIJING — Web users reported an outage of China's strict Internet controls, known as the Great Firewall, for several hours Monday morning, allowing them brief access to banned Web sites such as YouTube, Facebook and Twitter.
Cautious excitement spread on some social-networking platforms as hope flared that Internet freedoms suddenly were being expanded after months of intensifying scrutiny.
"It's finally unblocked, reasons unknown," wrote a blogger named EFanZh. "I hope nothing gets blocked anymore. I can't take it any longer."
But by the time many woke up, strict restrictions had returned. Error messages once again flashed across computer screens for sites blocked by the nation's censorship filter.
"It seemed just like a dream," said Michael Anti, a social critic and one of hundreds who tweeted about the development on Twitter.
Rumors abounded that the outage was due to maintenance work administered by Internet provider China Unicom. Others believed it had something to do with the heavy snow that blanketed northern China over the weekend.
China Unicom did not respond to requests for an interview, nor did Chinese officials overseeing online security. It was unclear if all of China experienced the outage or just some regions.