The investigator should escalate these concerns to the bank anti-money laundering officer, who is responsible for overseeing the implementation and effectiveness of the bank's AML/CFT policies and procedures, as well as ensuring compliance with relevant laws and regulations. The bank anti-money laundering officer can then decide on the appropriate course of action, such as conducting further investigation, reporting to the regulators, or terminating the relationship with the customer. The other options are not suitable for escalating these concerns, as they may not have the authority, expertise, or responsibility to handle such matters.
ACAMS, CAMS Examination Study Guide, 6th Edition, Chapter 4, pp. 113-114 FATF Guidance: The Role of Hawala and Other Similar Service Providers in Money Laundering and Terrorist Financing, October 20131, p. 19 Basel Committee on Banking Supervision, Sound management of risks related to money laundering and financing of terrorism, June 20172, p. 10

According to the Basel Committee on Banking Supervision's Customer Due Diligence for Banks, the compliance function should provide an evaluation of a bank's policies and procedures independent from its management. The compliance function is responsible for ensuring that the bank adheres to the relevant laws, regulations, and standards on customer due diligence, anti-money laundering, and combating the financing of terrorism. The compliance function should also monitor the implementation and effectiveness of the bank's customer due diligence policies and procedures, identify and report any breaches or deficiencies, and recommend corrective actions or improvements. The compliance function should have sufficient authority, independence, resources, and access to information to perform its duties effectively.
Customer due diligence for banks, Basel Committee on Banking Supervision, October 2001, paragraphs 55-56 CAMS Study Guide - 6th Edition, Chapter 6, page 172 CAMS Certification Exam Outline, Domain 3, Task 3.1, Skill 3.1.2 Anti-Money-Laundering Guidance: Basel Committee Consultative Paper ..., Office of the Comptroller of the Currency, February 2001, page 2

When a financial institution is requested to provide data and information to a law enforcement agency for matters related to the financing of terrorism, assistance cannot be refused on the grounds of tipping-off.
Tipping-off refers to disclosing to a customer or any third party that a suspicious activity report (SAR) has been filed. However, in this specific context, the obligation to provide information to law enforcement takes precedence over any concerns related to tipping-off. Financial institutions must cooperate fully with law enforcement agencies in such cases to combat money laundering and terrorist financing12.
References:
31 CFR 1010.520 (a) (2)
FinCEN: Fact Sheet on the Rapid Response Program (RRP)
FinCEN.gov
Federal Financial Institutions Examination Council (FFIEC) BSA/AML Examination Manual

Financial Intelligence Units (FIUs) are the primary channels for sharing financial intelligence both within countries and across borders. FIUs cooperate with each other and other relevant law enforcement, regulatory, or intelligence agencies in the fight against money laundering, terrorism financing, and other financial crimes.