Octomom -- Welfare Fraud Investigation in Full Swing

The investigation into whether or not Octomom committed welfare fraud has begun, and TMZ has learned authorities have started to contact her former employers to see just how much money she's been making.

As TMZ first reported, the L.A. County Dept. of Welfare Fraud Prevention and Investigation (WFP&I) was contacted by someone claiming that Octo is collecting welfare for her and her 14 kids despite allegedly making more than minimum amount required to collect welfare.

Octomom can receive welfare support if she made less than $119,000 in a calendar year because she had so many children, but authorities believe she may have made over $200,000.

According to our sources, investigators have begun calling people who have employed Octo in the last year to determine just how much she's been raking in -- which will include collecting things like bank statements, canceled checks and wire transfer receipts.

We're told the investigators have asked these employers if they know of any other people who have employed Octo lately ... and the employers have handed over a few names that investigators are following up with.