(Bloomberg) -- Fidelity Investments said it will start two additional zero expense ratio mutual funds.

The Fidelity Zero Large Cap Index Fund and the Fidelity Zero Extended Market Index Fund will be available to investors starting Sept. 18, Boston-based Fidelity said in a statement Wednesday.

In August, the firm created the industry’s first free index funds: the Fidelity Zero Total Market Index Fund and the Fidelity Zero International Index Fund. They gathered about $1 billion in their first month.

To contact the reporter on this story: Alan Mirabella in New York at amirabella@bloomberg.net

To contact the editor responsible for this story: Margaret Collins at mcollins45@bloomberg.net

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