San Diego startup Empyr, a marketing technology company, has raised $3 million in an equity round, according to a regulatory form filed with the U.S. Securities and Exchange Commission Wednesday.

Empyr, a sub-business of Jon Carder’s rewards platform company MOGL, develops technology that allows companies to track when online advertising leads to offline purchases.

The company has already raised $45 million in venture capital since the company’s inception in 2011.

This latest round comes from four investors, according to the SEC filing.

Late last year, Empyr announced that it had formed a partnership with review website Yelp. The two tech companies would allow businesses listed on the website to offer Yelp users cash back discounts on in-store purchases.