Lumber Liquidators is cratering after the CDC raised the cancer risk of the company's flooring

Lumber Liquidators Holdings Inc.'s shares were set to tumble on Monday after a revised US federal agency report showed people exposed to some types of the company's laminate flooring were three times as likely to get cancer as previously estimated.

The Centers for Disease Control and Prevention said Thursday that they estimated the risk of cancer to be six to 30 cases per 100,000 people, compared with the two to nine cases the CDC had estimated in a February 10 report. The CDC said the revised results were preliminary.

Lumber Liquidators' shares dropped by as much as 22% in early trading on Monday. Ahead of the market open, the stock was set for its biggest intraday percentage drop in six months.

The CDC said it had used an incorrect value to calculate ceiling height, which meant its estimates of the airborne concentration of cancer-causing formaldehyde were about one-third what they should have been.

CBS "60 Minutes" reported on Sunday it was alerted to the possibility that scientists had not converted feet to meters in some calculations.

Lumber Liquidators was not available for comment outside regular business hours. It had supported the recommendations of the CDC's previous report on the safety of flooring made in China between 2012 and 2014.

The company's shares and sales have been in a tailspin since March, when "60 Minutes" reported the retailer's laminates from China contained excessive levels of formaldehyde.

Up to Friday's close of $14.21, Lumber Liquidators' shares had risen 17.5% since the CDC's initial report. But they are still down 79% since the company had in late February last year warned of the CBS report.

Here's a chart showing the drop on Monday:

(Reuters editing by Savio D'Souza)