TEHRAN – Many Iranian Internet users were disappointed Tuesday morning to discover  that Facebook and Twitter were blocked once again after a short-lived spurt of unfettered access Monday.

On Monday evening, the social media sites suddenly became accessible without anti-filtering software for one of the first times since the sites were blocked following protests in the aftermath of Iran’s 2009 presidential election. Not all Iranians were able to load the sites, but access appeared to be particularly common in Tehran.

Authorities said Tuesday that access was opened to the sites as the result of a “technical glitch” that had been corrected. Internet users here report that the access they enjoyed Monday was the best they had experienced in years, and that the sites worked on various Internet service providers, including the country’s highly controlled mobile phone network.

While most users expressed their surprise and happiness at being able to access the sites directly, a common theme among status updates and tweets Monday night mentioned “Hassan’s key," a reference to a large key that became the symbol of new President Hassan Rouhani's recent electoral campaign.

None of the Facebook or Twitter accounts belonging to Iranian officials, which have been the subject of much discussion in recent days, mentioned the unblocking or subsequent re-blocking of the sites