US fast food giant McDonald's warned on Thursday that fears over the safety of European beef, which dragged first quarter profit down 16 per cent, would make its second three months the most challenging this year, the Financial Times reports. Michael Conley, the company's chief financial officer, said "uncertainty in Europe about BSE [mad cow disease] and foot and mouth will make it very difficult". The caution comes just a month after the world's largest fast food chain warned profits would be hit by the safety concerns over European beef, prompting analysts to cut forecasts. The region accounts for about a quarter of McDonald's total sales. McDonald's reported a disappointing $378.3m or 29 cents a share in the first quarter, compared with $450.9m or 33 cents a share a year ago. The result wasits second quarterly profit decline. Sales in Europe fell 6 per cent from $2.3bn to $2.18bn. European sales include France, Germany, Spain and Italy. Sales in the US market improved 4 per cent from $4.5bn in the year ago quarter to $4.6bn.