British police accessed BlackBerry messages and trawled Twitter for intelligence during last week's riots, a senior officer told MPs.
Police also considered turning off the mobile messaging service, but eventually decided not to try, MPs were told.
Social-media sites and mobile services - notably BlackBerry Messenger (BBM) - have been accused of being used to organise looting and rioting, with Prime Minister David Cameron saying the Government was looking into whether it could shut down such services during such incidents.
We did not request that that was turned off, but it is something that we are pursuing as part of our investigative strategy
Acting Metropolitan Police Commissioner Tim Godwin told MPs the force had considered shutting down BBM during the worst of the riots on Monday night in London.
"We did contemplate, I contemplated, asking the authorities to switch it off. The legality of that is very questionable and additionally it is also a very useful intelligence asset," he said.
"As a result of that, we did not request that that was turned off, but it is something that we are pursuing as part of our investigative strategy." Godwin would not expand on whether BlackBerry would be involved in any potential shut down.
Another senior officer told MPs that intelligence pulled from social networks as well as BBM helped avert trouble at the Olympic site in Stratford, as well as on Oxford Street and at Westfield shopping centre. "We were able to secure all those places and indeed there was no damage at any of them," said Assistant Metropolitan Police Commissioner Lynne Owens.
Messages shared via the BlackBerry network require PINs to be viewed, but according to a report in The Guardian the police accessed the messages using phones taken from those who had been arrested - speeding up a process that normally takes weeks.
BlackBerry had said at the time it was willing to help policing efforts during the riots. The company said it has no further comment.