Contaminated drops of condensation led to closure of a production line and the recall of Dreyer's ice-cream bars, a probe by the company has revealed. The listeria monocytogenes bacteria found in two ice-cream bars came from droplets which fell on to the production line in Dallas, Texas. The drops were contaminated with the bacteria commonly found in the environment, said Chris Atkins, commercial director of Dreyer's local distributor Mountain Cream International yesterday. 'We identified this as the most likely source,' he said, adding that Texan health officials and Food and Drug Administration representatives had joined the inquiry. Environmental testing within the factory had been increased 800 per cent and an intensified cleaning programme had been introduced. Dreyer's voluntarily recalled all their ice-cream products after routine Department of Health checks found two Cookies 'N Cream bars to be contaminated last month. The department said yesterday it would continue to hold and test for the bacteria in each Dreyer's consignment. A spokesman said the probe had been conducted in a thorough manner.