A hand grenade was found from the Sri Lanka Medical Council (SLMC) premises at Norris Canal Road, Colombo 10 on Saturday, Police said.
Police say the grenade must have been thrown into the SLMC premises but it had not exploded.
A Police team had arrived at the SLMC office after it received a call on the emergency hotline 119 around 6.45 am on Saturday.
Later, a team from the Police Special Task Force (STF) was called in and they had taken the grenade to the Grandpas Cemetery and defused it, Police media unit said. A special Police team is conducting a probe into the incident.