Generally speaking, you can't ask the public security organs to assist in investigating this evidence, because labor disputes belong to "economic disputes" and public security organs can never interfere in civil economic disputes; Unless the employer illegally employs workers, it violates the Law on Public Security Administration Punishment or the Criminal Law, which constitutes the crime of forced labor.
However, in labor arbitration, some evidence is in the hands of employers, and it is impossible for workers to provide it. According to the law, such evidence shall be provided by the employer, and if it cannot be provided, the employer shall bear the adverse consequences:
People's Republic of China (PRC) labor dispute mediation and arbitration law
Article 6
: "In the event of a labor dispute, the parties have the responsibility to provide evidence for their claims. If the evidence related to the disputed matter belongs to the management of the employer, the employer shall provide it; If the employer does not provide it, it shall bear the adverse consequences. "
Article 39
: "If the evidence provided by the parties is verified, the arbitration tribunal shall take it as the basis for ascertaining the facts. If the laborer is unable to provide the evidence related to the arbitration request controlled and managed by the employer, the arbitration tribunal may require the employer to provide it within a specified time limit. If the employer fails to provide it within the prescribed time limit, it shall bear the adverse consequences. "
I hope my hungry answer can help you!