Smokey Robinson is now the subject of a Los Angeles County Sheriff’s Department investigation after multiple women came forward and filed police reports alleging sexual assault … TMZ has learned.

Law enforcement sources tell TMZ … three alleged victims — all female — filed police reports against Smokey on Friday with the sheriff’s department. The department’s special victims’ unit has opened a criminal investigation into the claims. We’re told the investigation is in its early stages.

Our sources say investigators will reach out to Smokey to try to speak to him about all the allegations made against him in these police reports.

As you know … four Jane Does — all of whom claim they used to work as housekeepers for Smokey — filed a lawsuit against the star earlier this month, alleging sexual battery, assault, false imprisonment and gender violence, seeking millions in damages.

In the lawsuit, the four accusers claim they were sexually assaulted by Robinson multiple times. All of them claim Smokey would call them into his bedroom or other places while his wife was away from the house, where he would then force himself upon them.

Smokey’s attorney called the civil lawsuit an attempt to “extract money from an 85-year-old American icon” and called all of the allegations totally false.