Nearly 150kg of chemicals have been uncovered from a bus running on Ampara-Colombo route.
The haul contained in 5 sacks found at the Thiriwanaketiya roadblock in Ratnapura during a joint search mission by the Police and the Army.
Four suspects including a former Army officer have been arrested over the incident.
The police said the chemical haul would be directed to the Government Analyst after obtaining a court order.
Ratnapura Police is conducting further investigations into the incident.