They are known as "love-locks" and have made a mysterious appearance in Timaru.
Several of them appeared along with a sign at the pedestrian bridge on The Bay Hill overnight on Thursday.
No-one has put up their hand and claimed responsibility, but the The Herald understands love-locks or "love padlocks" are also popping up in Europe and Asia.
They started appearing on bridges in Europe about 10 years ago without any reason and without a source or origin.
Lovers engrave their initials on the padlocks and fasten them to railings, then throw away the keys.
Local authorities in several countries have tried to remove the padlocks.
In Paris on the Pont de l'Archeveche, a bridge that crosses between the Left Bank and Notre-Dame Cathedral on the Seine, thousands of love-locks reappeared in 2011 after mysteriously disappearing at night a year earlier. Paris Town Hall expressed concern in 2010, claiming the locks raised problems for the preservation of the city's architectural heritage.
In Taiwan it is widely reported that padlocks fixed to an overpass in the city of Fengyuan appear in pairs and are known as "wish locks". Local legend suggests that the magnetic field generated by passing trains creates energy in the locks and fulfils the wishes.
Taiwanese authorities have reportedly cleared the fence several times but new padlocks keep turning up.
- The Timaru Herald