A 40-year-old Mount Gambier man has been reported by South Australia Police after a concealed knife was allegedly discovered during routine security screening at the Mount Gambier Courthouse.

Police said the incident occurred at the courthouse on Bay Road after court sheriffs identified a credit-card-style knife concealed inside the man's wallet. Officers were called to the courthouse and spoke with the man following the discovery.

The knife was seized by police, and the man is expected to be summonsed to appear in court at a later date. Police reported the matter as an alleged offence involving the carrying of an offensive weapon.

Security screening at courthouses is designed to prevent weapons and other prohibited items from entering areas where court proceedings take place. The discovery highlights the role of court sheriffs in identifying potentially dangerous items before they enter the building.

The incident did not involve a reported confrontation or injury. Instead, the weapon was detected during the screening process, allowing authorities to intervene and remove it from the premises.

Credit-card-style knives are designed to be compact and easily carried, which can make them difficult to identify without appropriate security screening. In this case, court security staff detected the item concealed inside the man's wallet.

Police have seized the alleged weapon as part of the investigation. The man has not been convicted of an offence, and the allegation will be dealt with through the court process.

The incident is also a reminder that people attending South Australian courts are subject to security requirements. Items considered weapons or prohibited articles can be seized, and people found carrying them may face legal consequences.

The Mount Gambier Courthouse is an important part of the Limestone Coast's justice system, handling a range of legal matters involving residents from the region. Maintaining security at the courthouse is intended to protect court staff, legal professionals, witnesses, defendants and members of the public.

Police said the man will be summonsed to appear in court at a later date, where the matter can proceed through the appropriate legal process.

At this stage, there is no indication from police that the incident was connected to a broader security threat at the courthouse.

The investigation and legal proceedings will determine the circumstances surrounding the alleged possession of the knife and any applicable penalties.