The case, found just after 9pm on a train from Rheintal, was marked with hand drawn symbols indicating it contained explosives and the words “Danger, weapon”, according to St Gallen police.
It was later found to contain a set of kitchen knives.
“A passenger found the case on a seat and called the emergency services immediately,” a police spokesperson told 20 Minuten.
Following the discovery all the passengers were made to leave the train when it stopped in Rorschach and police then carried out a search.
“To avoid causing panic, the driver just told the passengers a police operation was underway,” the spokesperson said.
The owner of the case was traced thanks to the telephone number that was also found on the case.
Despite the Graubünden resident's assurances that the case contained only knives, the police were sceptical and insisted he open it himself.
The amateur chef told police he had forgotten the case when he left the train in Landquart.
He said he had put the warnings on it to deter his children from opening it and playing with the knives.
The man may face criminal charges, the police spokesperson said.