Surveillance and tracking of a person without the information thereof shall be performed, on the basis of a decision of an investigating judge, if there are grounds to believe that the behaviour of the person, or his or her contact with other persons, may contain information regarding facts included in circumstances to be proven, for a term up to 30 days which an investigating judge may extend, if necessary. An investigating judge shall indicate in a decision whether the rights are granted to continue with the surveillance and tracking, for a term of up to 48 hours, of other persons who have been in contact with a person to be placed under surveillance.