According to the police a suspect has now been arrested over the incident and was produced in court and remanded.
The monks fell ill on February 20th after eating food given to them at a temple in the area and were admitted to hospital, the police said.
According to the police investigations have now revealed that some kind of drug was mixed with the food which was given to them.
The Anuradhapura police said that they believed the suspect attempted to make the monks fall unconscious in order to rob the premises.
Further investigations are underway.