What began as a Connecticut investigation into Juul Labs Inc.’s marketing and sales practices has now turned into a 39-state probe into whether the California-based electronic cigarette company targeted minors, misled customers about nicotine content, and made false claims about its product’s effective as a smoking-cessation tool.

Connecticut, Texas, Florida, Nevada and Oregon are spearheading the investigation. They announced Tuesday that 34 other states have joined the effort. But Connecticut attorney general spokeswoman Elizabeth Benton declined to name the other states, saying some are barred from disclosing their investigations, while others plan to make announcements in due time.