65 Therefore, State authorities are obliged to collaborate in the collection of evidence to achieve the objectives of the investigation and refrain from acts that imply obstructions to the progress of the investigative process. 225 213. Given its importance, the obligation to investigate in the present case must be carried out in accordance with the international standards and jurisprudence that govern the investigation of serious human rights violations, which implies, in the first place, the creation of an adequate domestic regulatory framework and/or the organization of the system of administration of justice in such a way that it ensures that investigations are carried out ex officio, without delay and in a serious and effective manner. 226 214. Likewise, this duty entails the removal of any de jure and de facto obstacle that impedes the investigation and prosecution of the facts and, if applicable, the punishment of all those responsible for the violations declared, as well as the search for the truth. For this reason, in the instant case, which deals with serious human rights violations committed in a context of massive and systematic violations, the obligation to investigate cannot be dismissed or conditioned by domestic acts or regulations of any kind. 227 215. The Court also considers it pertinent to point out that the obligation to investigate, prosecute and, if appropriate, punish those responsible for human rights violations does not derive solely from the American Convention. In certain circumstances, and depending on the nature of the facts, this obligation also derives from other inter-American instruments that establish the duty of the States Parties to investigate conduct prohibited by such treaties. 228 In this regard, the Court notes that, in this case, the obligation of the State to investigate, assumed upon ratification of the American Convention and still in force today, was reaffirmed by Guatemala when it deposited the instrument of ratification of: i) the Inter-American Convention to Prevent and Punish Torture on January 29, 1987; ii) the Convention of Belém do Pará on April 4, 1995, and iii) the Inter-American Convention on Forced Disappearance of Persons (ICFDP) on February 25, 2000. Thus, the State should have ensured its compliance from that moment on, 229 even though said instruments had not been adopted by Guatemala at the time of the events of this case. 216. Furthermore, since in the instant case some persons were forced to work against their will (supra paras. 97 and 116), the Court recalls the imprescriptible nature of the crime of slavery and similar conditions in international law, given their nature as crimes under international law, whose prohibition has attained the status of jus cogens. 230 For these reasons, when the States become aware of an act that could constitute slavery or servitude in the terms of Article 6 of the American Convention, they must initiate ex officio the pertinent investigation for the purpose of establishing the corresponding individual responsibilities.231 217. As noted previously (supra paras. 121 and 122), the body of evidence shows that in this case an investigation was opened before the Unit for Special Cases and Human Rights Violations of the Public Prosecutor’s Office and another before the Human Rights Ombudsman in relation to Cf. Case of García Prieto et al. v. El Salvador. Preliminary objections, merits, reparations and costs. Judgment of November 20, 2007. Series C No. 168, para. 112, and Case of the Peasant Community of Santa Bárbara v. Peru, para. 237. 226 Cf. Case of Anzualdo Castro v. Peru, para. 65, and Case of the Massacres of El Mozote and Nearby Places v. El Salvador, para. 247. 227 Cf. Case of Contreras et al. v. El Salvador. Merits, reparations and costs. Judgment of August 31, 2011. Series C No. 232, para. 127, and Case of García Lucero et al. v. Chile. Preliminary objection, merits and reparations. Judgment of August 28, 2013. Series C No. 267, para. 149. 228 Cf. Case of the Rio Negro Massacres v. Guatemala, para. 222. 229 Cf. Case of the Miguel Castro Castro Prison v. Peru. Merits, reparations and costs. Judgment of November 25, 2006. Series C No. 160, para. 377, and Case of Massacres of El Mozote and nearby places v. El Salvador, para. 246. 230 Cf. Case of the Hacienda Brasil Verde Workers v. Brazil. Preliminary objections, merits, reparations and costs. Judgment of October 20, 2016. Series C No. 318, para. 454. 231 Cf. Case of the Rio Negro Massacres v. Guatemala, para. 225. 225