Mandla: Houses built on government land by 11 persons were demolished in tribal-dominated Mandla in Madhya Pradesh as part of action against the illegal beef trade in the state, a police official said on Saturday.The action was taken after a tip off was received that a large number of cows had been held captive for slaughter in Bhainwahi area in Nainpur, Mandla Superintendent of Police Rajat Saklecha told PTI.