Another individual has been arrested over investigations carried out into the discovery of a hand grenade at a private hospital in Narahenpita.
The suspect was arrested in Mahawa.
The Colombo Crimes Division said the suspect was found to be in possession of 18 live ammunition.
The hand grenade was found in a toilet on the first floor of the hospital on Wednesday.
Investigations revealed the hand grenade was placed by one of the two individuals who were arrested on the same day in relation to the incident.
The suspect had placed the hand grenade and had given the tip off himself, of the explosive with the objective of claiming a cash reward for this act.
Police said the safety of the hand grenade had been removed and the grenade was attached to a mosquito coil.