On a normal day, more than 25,000 packages pass through the logistics centre at Lieto, close by the city of Turku.
It is a hub for processing deliveries purchases from online merchants, and for postal packages headed out of the country.
An effort is being made to store packages as efficiently as possible, but it is fairly certain that soon the centre will run out of room.
"We will undoubtedly need more space by early next week. We know of one warehouse in an industrial park in Turku that will do - if the strike ends by Wednesday," says the centre's chief of production, Martti Väisänen.
Even if the strike is short-lived, clearing the backlog will take several days.
"I do believe, though, that presents bought online will be delivered in time for Christmas," Väisänen told Yle on Friday.