The short seller who called out Lumber Liquidators' formaldehyde problem is now targeting a furniture company

Hedge fund manager Whitney Tilson, the founder of Kase Capital, pitched two news ideas at the Robin Hood Investors Conference in New York on Monday.

The newest long in his portfolio is low-cost airline company Spirit Airlines.

But Tilson, who's famously short hardwood retailer Lumber Liquidators, is also betting against furniture company Wayfair.

Tilson said that he's had five items of Wayfair's furniture tested for formaldehyde and, of the three he's received results on, two showed toxic levels.

Of the products Tilson had tested, one is being sold on the websites for Walmart, Kohl's, Staples and Shop Your Way.

Tilson is the one who flagged the Lumber Liquidators formaldehyde issue for CBS "60 Minutes." Since that report aired in March, the stock has collapsed more than 72%.

We've reached out to a Wayfair representative for comment. So far, Wayfair's shares have held up under the scrutiny.

Here's Tilson's full 103 slide presentation: