(Reuters) - Australia's Boral Ltd BLD.AX said on Monday delays to building projects due to bushfires will likely cause a plunge in its second-half results, while revealing an investigation had found inflated earnings at its North American window-making business.

FILE PHOTO: The logo of Boral Ltd, Australia's biggest supplier of building products, adorns the side of a cement truck in Sydney, Australia, November 23, 2016. REUTERS/David Gray/File Photo

In a flurry of news, the building materials maker also said Chief Executive Mike Kane, at the helm for more than seven years, will retire after it reports full-year earnings in August.

Shares plunged more than 12% - their biggest one-day drop since the last major profit warning in August - wiping out nearly $500 million from the firm’s market valuation.

“Kane took the company to the U.S. and really threw the dice on major acquisitions there, which has actually failed on a lot of fronts,” said Henry Jennings, senior analyst and portfolio manager at Marcustoday Financial Newsletter.

“Now these accounting irregularities have come to light as well and that really has put the final nail in his coffin from a corporate perspective. I think it is time for a fresh set of eyes to look at this company.”

Boral said the real impact of the bushfires will be seen in the second-half of its financial year as infrastructure works suffer disruptions and as activity in the building sector slows.

It reported a A$1 million ($670,300.00) hit for its first six months from bushfires that have scorched huge swathes of land across Australia, destroying homes and killing people and animals.

Core earnings in fiscal 2020 is likely to be lower across its three divisions. It sees net profit after tax around A$320 million to A$340 million, a decline of as much as 38% from an adjusted A$440 million last year, factoring in the overstatement at the windows business.

Pre-tax earnings at the North American division were overstated by $24.4 million between March 2018 and October 2019, Boral said, adding the figures were within its previously advised range.

Boral is now overhauling the division, firing the vice president of finance and financial controller. It said the accounting overstatement was limited to the windows business.

The investigation found no evidence that the overstatement was to hide the theft, the company said.

“The board and management are deeply disappointed at the breach of trust that led to the accounts of the Windows business being misreported to inflate profitability,” Kane said in a statement.

In Monday’s earlier-than-expected announcement, Boral also said net profit after tax before significant items was A$156 million for the half year ended Dec. 31. It will give further details on the originally scheduled results date of Feb. 20 along with further outlook.

It also announced an interim dividend of 9.5 cents per share.