Accident on US 31 at 100 South. 10-50 PI accident. Lifeline Helicopter is enroute to the scene. Railroad is closed down along with southbound US 31. Command on scene is advising they have a small acid leak. Units on scene are Cicreo Twp. Fire Engine 21, Medic 22, Rescue 25,Medic 81. Lifeline Dispatch paged out Rotor 30 to the accident scene.Accident scene is 2 to 3 miles east of Tipton. Radio Traffic is on Tipton County Fire 154.980 and Lifeline Dispatch 155.160 Tues 3-20-12 7:05AM Update at 9:32AM. This was a Haz-Mat accident. A semi hit a box truck from the rear that was hauling haz mat cargo. A haz-mat unit from Howard County is on scene and US 31 northbound and southbound are closed. Radio Traffic from ISP Peru Post 16 is advising that US 31 could be closed for 4-5 hours for the clean up.