QUETTA-Four government schools including two girls schools have been closed down in Quetta for indefinite period on Friday after receiving threatening letters by their management sent by banned militant organisation Baloch Liberation Army (BLA) and Tahrik-e-Taliban Balochistan (TTB). The police sources while confirming the closure of four govt schools said that these schools include Girls High School Killi Shiekhans, Central High School for Boys, Sariab Mill High School for Boys and Girls High School Muno Jan Road. The police sources said that the Principal of Girls High School Killi Shiekhans received a hand written letter two days ago, warning Principal and teachers not to teach them obscenity and behave like honourable Islamic women observing veil. It says that Tehrik-e-Taliban Balochistan had its informers among them from girl students and teachers who keep it informed about the interior atmosphere of the school. It further said: 'do not put TT Balochistan on trial and behave properly ,otherwise, the organisation would have no option except to take action against those who were involved in teaching obscenity in the school and polluting the atmosphere. The sources further said that after receiving the threatening letters, the management of schools of girls Muno Jan Road, and two boys schools Sariab Mill and central was closed for indefinite period. They say that in the letters bearing the name of banned Baloch Liberation Army (BLA), it threatened to start attacks against non-local teachers for the actions of security forces in Quetta and others parts of the province against Baloch population. It also says that non-local teachers should immediately leave Balochistan if they want to avoid such armed attacks. No official version of administration or Education Minister was available immediately.