Apparatus, comprising at least one processor, at least one memory including computer program code, and the at least one processor, with the at least one memory and the computer program code, being arranged to cause the apparatus to at least perform at least distributing (S10) respective location data of a plurality of users into respective buckets for each of the users, wherein each of the location data indicates a location of the respective user at a time during a predetermined time period, each of the buckets includes a respective time interval of the time period, the time intervals do not overlap and cover the time period, the time intervals are the same for all of the users, and there is a bucket for each of the users for each of the time intervals; calculating (S20), for each pair of the users and for each of the time intervals, a respective sub-distance between the users of the respective pair based on the location data in the respective buckets; aggregating (S30), for each of the pairs of the users, the sub-distances over the time period to obtain a distance between the users of the respective pair; clustering (S40) the users having a closest distance from each other in order to obtain respective clusters of the users, checking if a number of the users in the respective cluster is larger than a predetermined number; determining a first cell where the number of the users in the respective cluster is larger than the predetermined number; providing an information to the users via cell broadcast in the first cell if the number of the users in the respective cluster is larger than the predetermined number; and providing the information to the users by a dedicated message if the number of the users in the respective cluster is not larger than the predetermined number. distributing (S10) respective location data of a plurality of users into respective buckets for each of the users, wherein each of the location data indicates a location of the respective user at a time during a predetermined time period, each of the buckets includes a respective time interval of the time period, the time intervals do not overlap and cover the time period, the time intervals are the same for all of the users, and there is a bucket for each of the users for each of the time intervals; calculating (S20), for each pair of the users and for each of the time intervals, a respective sub-distance between the users of the respective pair based on the location data in the respective buckets; aggregating (S30), for each of the pairs of the users, the sub-distances over the time period to obtain a distance between the users of the respective pair; clustering (S40) the users having a closest distance from each other in order to obtain respective clusters of the users, checking if a number of the users in the respective cluster is larger than a predetermined number; determining a first cell where the number of the users in the respective cluster is larger than the predetermined number; providing an information to the users via cell broadcast in the first cell if the number of the users in the respective cluster is larger than the predetermined number; and providing the information to the users by a dedicated message if the number of the users in the respective cluster is not larger than the predetermined number. <EOS>