29 C.F.R. § 1991.104 – Investigation.

(a) OSHA will notify the respondent(s) and the complainant's employer (if different) of the filing of the complaint, of the allegations contained in the complaint, and of the substance of the evidence supporting the complaint. Such materials will be redacted, if necessary, consistent with the Privacy Act of 1974, 5 U.S.C. 552a, and other applicable confidentiality laws. OSHA will also notify the respondent of its rights under paragraphs (b) and (f) of this section and § 1991.110(e). OSHA will provide an unredacted copy of these same materials to the complainant (or the complainant's legal counsel if complainant is represented by counsel) and to the DOJ.
(b) Within 20 days of receipt of the notice of the filing of the complaint provided under paragraph (a) of this section, the respondent may submit to OSHA a written statement and any affidavits or documents substantiating its position. Within the same 20 days, the respondent may request a meeting with OSHA to present its position.
(c) During the investigation, OSHA will request that each party provide the other parties to the whistleblower complaint with a copy of submissions to OSHA that are pertinent to the whistleblower complaint. Alternatively, if a party does not provide its submissions to OSHA to the other party, OSHA generally will provide them to the other party (or the party's legal counsel if the party is represented by counsel) at a time permitting the other party an opportunity to respond. Before providing such materials to the other party, OSHA will redact them, if necessary, consistent with the Privacy Act of 1974, 5 U.S.C. 552a, and other applicable confidentiality laws. OSHA will also provide each party with an opportunity to respond to the other party's submissions.
(d) Investigations will be conducted in a manner that protects the confidentiality of any person who provides information on a confidential basis, other than the complainant, in accordance with 29 CFR part 70.
(e)
1. (1) A complaint will be dismissed unless the complainant has made a prima facie showing that a protected activity was a contributing factor in the adverse action alleged in the complaint.
2. (2) The complaint, supplemented as appropriate by interviews of the complainant, must allege the existence of facts and evidence to make a prima facie showing as follows:
  1. (i) The individual engaged in a protected activity;
  2. (ii) The respondent knew or suspected that the individual engaged in the protected activity;
  3. (iii) The individual suffered an adverse action; and
  4. (iv) The circumstances were sufficient to raise the inference that the protected activity was a contributing factor in the adverse action.
3. (3) For purposes of determining whether to investigate, the complainant will be considered to have met the required burden if the complaint on its face, supplemented as appropriate through interviews of the complainant, alleges the existence of facts and either direct or circumstantial evidence to meet the required showing, i.e., to give rise to an inference that the respondent knew or suspected that the individual engaged in protected activity and that the protected activity was a contributing factor in the adverse action. The burden may be satisfied, for example, if the complainant shows that the adverse action took place shortly after the protected activity. If the required showing has not been made, the complainant (or the complainant's legal counsel if complainant is represented by counsel) will be so notified and the investigation will not commence.
4. (4) Notwithstanding a finding that a complainant has made a prima facie showing, as required by this section, further investigation of the complaint will not be conducted if the respondent demonstrates by clear and convincing evidence that it would have taken the same adverse action in the absence of the complainant's protected activity.
5. (5) If the respondent fails to make a timely response or fails to satisfy its burden set forth in the prior paragraph, OSHA will proceed with the investigation. The investigation will proceed whenever it is necessary or appropriate to confirm or verify the information provided by the respondent.
(f) Prior to the issuance of findings and a preliminary order as provided for in § 1991.105, if OSHA has reasonable cause, on the basis of information gathered under the procedures of this part, to believe that the respondent has violated CAARA and that preliminary reinstatement is warranted, OSHA will contact the respondent (or the respondent's legal counsel if respondent is represented by counsel) to give notice of the substance of the relevant evidence supporting the complainant's allegations as developed during the course of the investigation. This evidence includes any witness statements, which will be redacted to protect the identity of confidential informants where statements were given in confidence; if the statements cannot be redacted without revealing the identity of confidential informants, summaries of their contents will be provided. The complainant will also receive a copy of the materials that must be provided to the respondent under this paragraph. Before providing such materials, OSHA will redact them, if necessary, consistent with the Privacy Act of 1974, 5 U.S.C. 552a, and other applicable confidentiality laws. The respondent will be given the opportunity to submit a written response, to meet with the investigator, to present statements from witnesses in support of its position, and to present legal and factual arguments. The respondent must present this evidence within 10 business days of OSHA's notification pursuant to this paragraph, or as soon thereafter as OSHA and the respondent can agree, if the interests of justice so require.