exhaustion of domestic remedies, it is up to the State to demonstrate that the domestic remedies have not been exhausted, unless that is clearly evident from the record. 44. In situations such as the one described herein, the case law of the inter-American system has established that the State that alleges that its domestic remedies have not been previously exhausted must, before approaching the international system of protection, indicate the appropriate remedies to rectify the damages and provide proof of their effectiveness. 56 45. As regards the writ of amparo filed by the petitioners, the IACHR considers that this recourse is equivalent to a writ of habeas corpus under Mexican law. In this case, the IACHR notes that this writ was filed for the purpose of learning the whereabouts of the alleged victim, but it was rejected in limine because it did not provide information that would make it possible to establish the place where Antonio González Méndez was presumably being detained. Therefore, the IACHR is of the view that despite the fact that habeas corpus is the adequate recourse to determine the whereabouts of a presumably disappeared person, in the present case, this recourse was not capable of guaranteeing the protected right for which it was conceived, and for this reason the petitioners opened a pretrial investigation. On this matter, the Inter-American Court has maintained that “use of the remedy of habeas corpus does not rule out a possible criminal proceeding based on the information sought in it.” 57 46. The Commission holds that states, pursuant to their international obligations, have the duty to investigate incidents denounced and, if appropriate, to prosecute the responsible parties. In the procedure before the Commission, the State did not justify why the investigations remain open in their initial stage, even though that is part of its obligations. On this point, the Inter-American Court has upheld that “the duty to investigate is an obligation of means, not results. It must be performed by the State as one of its duties under the law, and not as a mere formality doomed in advance to be unproductive.” 58In other words, “[...] once State authorities take cognizance of a matter, they must ex officio and without delay, conduct a serious, impartial, and effective investigation.” 59 47. Without prejudice to the merits of the case, the IACHR concludes that the writ of amparo filed by the petitioners was the appropriate recourse to locate the whereabouts of a presumably disappeared person. However, in the case under consideration, that recourse proved to be ineffectual, due to the requirement stipulated in Mexican legislation that the place of detention be indicated. The Commission further notes that in this case, the petitioners filed a complaint with the Mexican authorities, which opened pretrial investigation AL/41/SJI/030/99, which is 56 IACHR, Report Nº 55/06, petition 12.380, Admissibility, Members of the “José Alvear Restrepo” Collective Corporation of Attorneys, Colombia, July 20, 2006, para. 36; Report Nº 32/05, petition 642/03, Admissibility, Luis Rolando Cuscul Pivaral and other persons affected by HIV/AIDS, Guatemala, March 7, 2005, paras. 33-35; I/A Court H.R., Case of the Mayagna (Sumo) Awas Tingni Community, Preliminary Objections. Judgment of February 1, 2000. Series C No. 66. para. 53; Durand and Ugarte Case, Preliminary Objections. Judgment of May 28, 1999. Series C No. 50, para; and, Cantoral Benavides Case, Preliminary Objections. Judgment of September 3, 1998. Series C, No. 40, para. 31. 57 I/A Court H.R., Case of the Serrano Cruz Sisters. Judgment of March 1, 2005. Series C, No. 120, para. 82. 58 I/A Court H.R., Case of Penal Miguel Castro Castro. Judgment of November 25, 2006, Series C No. 160. para. 255; Case of Ximenes Lopes. Judgment of July 4, 2006. Serie C No. 149, para. 148; Case of the Ituango Massacres, judgment of July 1, 2006. Series C No. 148, para. 296; Case of Baldeón García. Judgment of April 6, 2006, Series C No. 147, para. 93. 59 I/A Court H.R., Case of Penal Miguel Castro Castro. Judgment of November 25, 2006. Series C No. 160. para. 256; Case of Goiburú et al. Judgment of September 22, 2006. Series C No. 153, para. 117; Case of Baldeón García. Judgment of April 6, 2006, Series C No. 147, para. 93; Case of fthe Massacre of Pueblo Bello. Judgment of January 31, 2006. Series C No. 140, para. 144. 11