Four teachers from Madhya Pradesh were killed early on Monday while returning from a tour of Agra, police said.A group of eight teachers travelling in an SUV met with an accident around 5.30 a.m. when their vehicle rammed into a truck stationed on the roadside in Madhya Pradesh's Shivpuri district, police Inspector Rajesh Tripathi said.Four were critically injured in the disaster on the Agra-Mumbai highway. All eight were from Sehore district.The deceased were identified as Bharat Singh, Vishnu Sen, Ramesh Chandra Rai and Makhan Singh.