The BBC's website, bbc.co.uk, went offline for almost an hour last night. The corporation's press office, clearly taken by surprise, said: "We apologise for the loss of BBC Online. We are looking into it."

But just as millions of users started to look for the Ceefax button on their remote controls, the site was back. Nevali, described as a "metadata magician at the BBC", tweeted: "it's not a DoS [Denial of Service] attack. routing went away. software config or hardware problem."

It didn't take long for the Twitterverse to catch light with conspiracy theories. "So the entire BBC website is offline – a glimpse of the future if the Murdochs and their pals, David Cameron & Jeremy Hunt, have their way," wrote DickMandrake.

GaryDelaney added: "I don't believe all these rumours about the BBC website being down. There's nothing about it on the BBC website."

Peter Horrocks, director of the BBC World Service, tweeted: "We're having technical problems with the BBC website – they are being looked into urgently. Apologies from BBC News."

But the rumours continued, given fuel by the news this January that the BBC had confirmed it would cut its online budget by 25%, or £34m. Some of the more outlandish rumours claimed that "Aunty" might have been attacked by the collective known as Anonymous.

Some time later, Steve Herrmann, editor of the BBC news website, said in a blog post: "It's not often we get a message from the BBC's technical support teams saying, 'Total outage of all BBC websites'.

"But for getting on for an hour this evening, until just before midnight, that's what happened. We haven't yet had a full technical debrief, but it's clear it was a major network problem.

"We'd like to apologise to everyone who couldn't get onto the BBC News website during that time."

The sprawling network of websites, known collectively as BBC Online, launched in 1997. Last year, the BBC said it was investigating after members of the public said they could not access the World Cup and Wimbledon live streaming. Others could not access the site at all – getting a 500 internal server error instead.

In 2009, similar problems appeared to afflict the site. On that occasion, the BBC said it was caused by a network failure that slowed down access to the site and had prevented some people from visiting its home page.