A magnet fisher checking a river for objects of interest had to call the police after explosives were pulled out of the water.
Suffolk Police said it closed a section of the B1064 at Long Melford on Saturday after the railway track explosives were discovered.
It is thought they were leftovers from the dismantling of the line to Bury St Edmunds in the 1960s.
An Explosive Ordanance Disposal team took the devices away.
The Sudbury and Haverhill Police team said the fisher was operating from a bridge and also found a knife, some shotgun cartridges and a BB gun, but it was the explosives that triggered the road closure.
It said the area still had "disused railway status".
The line was closed as part of
Dr Beeching's branch line closures.