Here, 'had informed' in past perfect tense is correct because it indicates a completed action of the past that happened before another event took place. Here, after the mother 'had informed the police, the DSP ordered the probe.
'Has informed' in present perfect tense is incorrect because it is used to indicate a past action which is not defined by a time of occurrence.
'Has been informed' in present perfect continuous tense is incorrect because it is used to indicate an action that started at some point in the past and may or may not be complete.