Two incidents in which live eels were hung from a rail bridge and hit by trains are being described as bizarre.
Drivers on Dunedin's Taieri Gorge Railway report the eels were hung from the Abbotsford bridge and were killed on impact.
Operations manager Grant Craig said hanging things from bridges has been happening for years, like sleepers or concrete blocks, but never live animals.
He said groups of teenagers were seen running from the scenes.
The incidents have been reported to the police.