The condition of the two IDF soldiers from the Tzukei Uvda army base, who had been hospiltized with severe pneumonia, remained serious on Monday morning. The condition of three other soldiers was defined as stable. Chief IDF Medical officer, Brig.-Gen. Hezi Levy, told Channel 2 Sunhjday evening that, "We have disregarded water pollution as a possibility for the outbreak. Probably one soldier was sick and due to the close-quarter living conditions on the base the virus spread quickly." Levy also completely disregarded rumors that a possible biological warfare attack may have been the cause of the outbreak, and said that the possibility of SARS or a bird-flu virus were equally as preposterous. A woman soldier - who also was part of a group of soldiers who contracted pneumonia at the Tzukei Uvda base in the south - was in serious condition at Soroka University Medical Center in Beersheba. She was previously in critical condition, but she has been stabilized. Five hundred recruits at the Tzukei Uvda base were given an unexpected holiday leave this week after the IDF Medical Corps ordered a quarantine following a fast-spreading outbreak of a serious lung infection. IDF sources said that training at the base was expected to begin again next week after final results of medical tests are received. The public health branch of the Medical Corps carried out a number of tests at the base in order to try and isolate the cause of the outbreak. The water and sewage systems at the base were closely examined, as were the showers and the air conditioning units. Still, as of Sunday morning, the cause of the outbreak was yet to be determined. "The IDF Medical Corps has opened an investigation into the circumstances surrounding the development of the disease," said the army spokesman. "In a place where there is a high concentration of people in one room or in a room that isn't sufficiently ventilated, there is close contact between people, which enables the passing of bacteria among people through saliva," said Professor Mordechai Kramer, director of the institute for lung disease at Rabin Medical Center. "One person breathes on a friend, or coughs in his direction, drops of saliva are passed and he is infected." The Ministry of Health was asked to check the possibility of similar cases throughout the country, especially in the south. Thus far, no such incidences were reported. At the beginning of last week, 14 soldiers from the base were hospitalized after contracting the infection. The soldiers initially complained of breathing problems and fever. While taken from their base to Eilat's Yoseftal Hospital, five of the soldiers were airlifted to Soroka Medical Center in Beersheba. Army medics who accompanied the sick from Eilat wore facemasks in order to prevent infection. One of the recruits was still hospitalized Sunday in serious but stable condition. Another four soldiers were still hospitalized in good condition, one of whom had suffered damage to both lungs. The three others had reportedly each suffered damage to one lung. "They have been transferred from an intensive care unit to the internal medicine wing," said an IDF spokesman. Eric Shechter and JPost staff contributed to this report.