BEIRUT (Reuters) - FIVE prisoners escaped from Lebanon's biggest jail on Saturday, using bedsheets to climb down a wall and then mingling with prison visitors before getting away, police said. Security sources said four of them were believed to belong to the Fatah al-Islam group which fought fierce battles with the Lebanese army in a Palestinian refugee camp in 2007. The Internal Security Forces said in a statement the five men, from Mauritania, Kuwait, Syria and Lebanon, escaped from Roumieh prison complex east of Beirut shortly before midday on Saturday. A sixth prisoner was caught as he tried to flee with them. Four months ago two Roumieh inmates died in a riot by prisoners protesting against overcrowding. The jail was built to hold 1,500 inmates but is now crammed with over 3,000 prisoners.