What looked to George Frazis a month ago as a core strength of the Bank of Queensland could soon be revealed as a powder-keg on the company's balance sheet.During a strategy presentation in February, the new BoQ chief identified the bank's fast-growing business lending operation as a key driver of future growth.At that briefing Frazis disclosed that his bank was continuing to expand business lending faster than its regional banking peers and most of the major banks. The latest monthly statistics published by APRA support his claim. In the 24 months to the end of February this year, BoQ's lending to businesses operating outside the financial sector increased by more than A$1.6 billion or 17 per cent to $11.25 billion.In the same period, the mortgage book expanded by only $900 million or 3 per cent to $28.7 billion.Given the dramatic impact of the COVID-19 crisis on Australian business activity in the last few weeks, BoQ is particularly exposed because the regulator's official data shows that around 27 per cent of its $41 billion loan book is at risk with SME borrowers.In comparison, Bendigo Bank has about $14 billion at risk with business customers, representing around 23 per cent of its total lending.Suncorp is even more conservatively positioned - its $12 billion business book accounts for 20 per cent of its overall credit exposure.The composition of the regional banks' business books are bit of mystery because none of them publish tables in their financial reports showing how their credit risk is spread across industry sectors.However, there is concern among investors that BoQ might have disproportionate credit exposure to several industries hard hit by COVID-19.Peppered throughout recent financial reports the bank describes its approach to business lending as one focused on selected niche industry markets where it has acquired a deep understanding of customers and credit risks.In the 2019 annual report those segments were named as the  tourism, hospitality, agribusiness and healthcare/retirement living industries.The risk in following such a "specialist" or "niche" lending strategy is that it could have led the bank to acquire concentrated exposure to one or more of the sectors that have borne the brunt of COVID-19.While BoQ states in its 2019 annual report that its business book is diversified geographically, it will be Frazis' job at the 2020 interim results announcement tomorrow morning to explain how exposed the bank is to the Queensland tourism and hospitality sectors.At the February strategy briefing BoQ's management reiterated the bank's focus on tourism and hospitality, describing the  two industries as "areas of current strength".Property development and healthcare services were identified as the other areas of similar standing in the business lending portfolio.BoQ's ramp up of business lending in recent times was driven by softening demand in the housing market throughout 2018 and the first of half of last year.From at least January 2018 BoQ struggled to sustain growth in residential mortgages as a swathe of sharply priced non-banks reclaimed market share from prudentially regulated lenders.During this period the Brisbane-based bank sought to