COLOMBO - Nineteen people including 12 military personnel were injured on Wednesday in an explosion on a bus in Sri Lanka, said the military, adding they do not know the cause but suspect it may be a bomb or grenade.Since the end of Sri Lanka's nearly three-decade civil war in 2009 there have been no targeted attacks on the military."There had been an explosion in a passenger bus. There are some fragments on the body of the bus. We suspect it as a bomb blast," military spokesman Sumith Atapattu told Reuters."The investigations underway to find out the details."Atapattu said seven army and five air force personnel along with seven civilians were injured in a fire following the explosion on the passenger bus which operated from northern Jaffna peninsula to central town of Diyathalawa, where one of the main military training centres is located.Sri Lanka ended a 26-year separatist war in May 2009 defeating Liberation Tigers of Tamil Eelam (LTTE) who fought to carve out a separate state for ethnic minority Tamil's in the far north of the Indian ocean island nation.Tamil Tiger rebels commonly used Improvised Explosive Devices (IEDs) to target civilians and military personnel during the civil war, which killed at least 100,000 people.