TITLE I
PERSON AND SOCIETY
CHAPTER I
FUNDAMENTAL RIGHTS OF THE PERSON
Article 2
g. No one shall be held incommunicado, except in cases where it is considered indispensable for clarifying a crime and in the form and for the time provided by law. The authority is obliged by law to report without delay and in writing, the place where the individual under arrest is being held.
Rights during investigation - arbitrary arrest or detention and deprivation of liberty
EDIT.