Analysis of more than 2.5m Twitter messages relating to the riots in England has cast doubt on the rationale behind government proposals to ban people from social networks or shut down their websites in times of civil unrest.

A preliminary study of a database of riot-related tweets, compiled by the Guardian, appears to show Twitter was mainly used to react to riots and looting.

Timing trends drawn from the data question the assumption that Twitter played a widespread role in inciting the violence in advance, an accusation also levelled at the rival social networks Facebook and BlackBerry Messenger.

The unique database contains tweets about the riots sent throughout the disorder, which began in Tottenham, north London, on 6 August. It also reveals how extensively Twitter was used to co-ordinate a movement by citizens to clean the streets after the disorder. More than 206,000 tweets – 8% of the total – related to attempts to clean up the debris left by four nights of rioting and looting.

The home secretary, Theresa May, will meet representatives from Facebook, Twitter and Research in Motion, the Canada-based BlackBerry maker, on Thursday. The companies said they would warn ministers against introducing emergency measures that could usher in a new form of online censorship.

Amid a growing censorship row, government sources said the home secretary did not expect to discuss closing social networks, but wanted to explore what measures the companies could take to help contain future disorder, including how law enforcement agencies can use the sites more effectively.

David Cameron had previously indicated he would contemplate more restrictive measures. The day after the riots subsided, the prime minister told parliament the government was looking at banning people from using sites such as Twitter and Facebook if they were thought to be plotting criminal activity. Cameron said the government would do "whatever it takes" to restore order, adding that a review was under way to establish whether it would be right to attempt to prevent rioters from using social networks. He said he had also asked police if they needed new powers.

The Metropolitan police later revealed it had considered switching off social networks during the disorder in London, but had decided not to on legal advice.

The Guardian database, which contains riot-related tweets sent between midnight on 6 August – the day riots began in Tottenham – and 8pm on 17 August, will be subject to more advanced analysis in the coming weeks as part of an ongoing investigation into the riots.