Iranians' sudden direct access to Facebook and Twitter was down to a technical fault, an Iranian official said on Tuesday, denying suggestions the government had lifted a ban on social media after four years, as the firewall that prevented access went back up. On Monday evening, several Iranians said they gained access to their accounts without having to get round a government firewall, leading them to hope that authorities had relaxed a ban in place since anti-government protests in 2009, some of which were organized on social media.But Abdolsamad Khoramabadi, secretary of a state committee tasked with monitoring and filtering sites, said technical difficulties with some Iranian Internet service providers (ISP) had allowed the access, and the government was investigating."The lack of a filter on Facebook last night [Monday] was apparently due to technical problems and the technological committee is investigating this issue," Khoramabadi was quoted by Mehr news agency as saying."We are investigating to see which of these companies has done this," he said, referring to the Iranian ISPs.One Iran expert based abroad said controls had briefly been removed across a very wide range of sites, including online pornography, supporting the view that it was a glitch.Another, however, said President Hassan Rouhani's new administration could be considering easing restrictions on sites that remain popular among Iranians able to get around the domestic firewall - and which senior government figures, and even Iran's clerical Supreme Leader, have themselves used to convey their messages."I strongly believe it was a technical glitch because all Web sites that support SSL were available in the country last night, even porn websites," said Amin Sabeti, a British-based expert on the Internet in Iran. SSL is a Web security tool. Sabeti added: "Iran has invested millions of dollars for its filtering system and it is clear that the regime will not give up Internet censorship very easily."Nonetheless, there have been signs in that direction. Rouhani, a moderately reformist cleric, pledged to relax some social controls during his campaign for June's election. New, US-educated foreign minister, Mohammad Javad Zarif, has Facebook and Twitter profiles and has engaged with other users. An account claiming to belong to Rouhani has also emerged on TwitterEven Supreme Leader Ayatollah Ali Khamenei seems to have taken to global social media to publicize ideas.Siavush Randjbar-Daemi, who lectures on Iran at England's Manchester University, said at least partially unblocking sites like Facebook would recognize its popularity. A ban on video recorders, he noted, was lifted in the 1990s when the devices had already become very widely used, despite being outlawed."Keeping them illegal became senseless," he said.Many Iranians use proxy servers to trick systems into believing they are outside Iran to access foreign social media.Randjbar-Daemi said the authorities might experiment with ways of allowing most access to the likes of Facebook and Twitter, as they do with the search site Google, while using technology to block certain kinds of activity. "I think we could be seeing a partial unblocking of Facebook, along the lines of Google, in which some search results are filtered but others are not," he said. "Rouhani would also score clear kudos within his supporters in this way."Arash Tajik, an IT administrator in Tehran, said he believed that the brief opening might have been part of an experiment by the authorities: "They are testing what will happen if they remove the filter and whether they can control the situation or not," said Tajik, who accessed Facebook unfiltered on Monday.Like Tajik, another Internet user in Tehran called Hossein, said he could not use Facebook without a proxy server on Tuesday. Hamed, a 32-year-old journalist and teacher, said he too found Facebook and Twitter blocked on Tuesday, said Internet providers could face penalties if the opening was unauthorized.Iran has accused Israel and the United States of cyberwar against its computer systems in the past, notably involving its energy and nuclear facilities. It did not link this week's brief failure of its social media firewall to hacking activity.Though Rouhani has spoken of reform, any move to ease controls will need approval from the ruling establishment of conservative clerics and security officials, including Khamenei.