Following the formal festivities for several employees of the Jämtland county council, five of the workers ventured into a nearby fire station garage where a reserve ambulance was stored.
They then proceeded to empty two canisters of nitrous oxide in the ambulance, rendering the vehicle unusable, according to local media reports.
Inga-Lill Persson, head of emergency care at Östersund hospital called the stunt “indefensible”.
“It shows extremely poor judgment,” she told the local Östersunds-Posten newspaper.
“An ambulance should be cleaned and everything should be in order so that you can head out quickly. That was not the case here.”
An internal investigation is underway and the five workers, all of whom have admitted to their involvement in the incident, risk being fired as a result.
One employee who was involved in a similar incident previously has also been suspended.
“Naturally, it's just as forbidden to hold a party in an ambulance garage as it is to hold one in an ambulance,” said Jämtland county council human resources chief Björn Ahlnäs in a statement.