29 CFR § 1960.29 - Accident investigation.
(a) While all accidents should be investigated, including accidents involving property damage only, the extent of such investigation shall be reflective of the seriousness of the accident.
(b) In any case, each accident which results in a fatality or the hospitalization of three or more employees shall be investigated to determine the causal factors involved. Except to the extent necessary to protect employees and the public, evidence at the scene of an accident shall be left untouched until inspectors have an opportunity to examine it.
(c) Any information or evidence uncovered during accident investigations which would be of benefit in developing a new OSHA standard or in modifying or revoking an existing standard should be promptly transmitted to the Secretary.
(d) The investigative report of the accident shall include appropriate documentation on date, time, location, description of operations, description of accident, photographs, interviews of employees and witnesses, measurements, and other pertinent information. A copy of the investigative report required by this section shall be forwarded to the official in charge of the workplace, the appropriate safety and health committee, and the exclusive employee representative, if any. The investigative report shall be made available to the Secretary or his authorized representative on request.