Twitter users revealing the locations of police drink-driving checkpoints in Mexico city could face prosecution, authorities say.
Mexico City public safety department spokesman Julio Iver said it was illegal for anyone to "divulge privileged information on police agencies", but he did not say what sanctions the Twitter users could face.
Mexico City police change the location of the breath-test checkpoints each day to discourage drink-driving.
Police cannot do roving tests from their patrol cars because the city requires that a doctor be present to administer the examinations.
A Twitter account has been tweeting the location of the checkpoints since at least December, apparently allowing motorists to avoid them.
Called "Anti Breath Test", the account now has over 3,400 followers.
The city's criminal code sets out fines of $455 to $2,270, and jail terms of six months to five years, for anyone who "in any way assists a criminal in avoiding investigation by legally constituted authorities or in escaping from them".
As of Monday, the account continued to be active, with tweets from users with nicknames like "drinkspiration" warning about checkpoints and criticising the police threat of prosecution.