Agony is being layered upon agony at Powerscreen International, the Northern Ireland engineering and heavy duty machinery company, trapped in the black hole of £47 million provisions set against accounting "irregularities" at its subsidiary, the Gloucester tractor supplier Matbro and at Matbro Northern Ireland .

It was learned this week that the British Serious Fraud Office is investigating the Matbro debacle following the referral of a report from the Department of Trade and Industry. The SFO says the Matbro mess, which involves mispricing of machines, unauthorised discounts and irregular methods of billing, "satisfies our criteria for cases". Powerscreen pledges "every assistance " to the SFO in its investigations. Last week Powerscreen agreed to sell Matbro to US equipment maker John Deere for £7 million sterling.

Powerscreen, the second largest public company in Northern Ireland, saw almost half of the stock market value disappear on January 27th last, the day that difficulties in the Matbro subsidiary were revealed. Investors, who provided £18 million via a share placing in December, will be anxious to learn if the group's board knew of the difficulties in Matbro at the time of the placing. The shares, now languishing at 190p, were valued at around 762p last October.