Police said the bridge crossing a construction site in Espoo’s Tapiola district collapsed mid-morning.
No one was killed but around 27 people are thought to have been injured, 10 of them seriously.
Espoo is a neighbouring city of Finland’s capital, Helsinki.
“Several people fell a few metres when the bridge collapsed. The situation is being investigated,” police said.
Helsinki University Hospital is treating 15 of those who were hurt.
“The injuries are mostly extremity fractures,” the hospital said in a statement, adding that the injured were part of a school group.
Finnish President Sauli Niinisto tweeted: “Shocking news about an accident in Tapiola. Providing support and help now important.”
Officers are conducting a technical investigation in the area in a bid to find the cause of the accident.
