By Essi Lehto

HELSINKI (Reuters) -Twenty-seven people, most of them teenage school children, were injured on Thursday when a temporary pedestrian bridge collapsed in the Finnish city of Espoo, just outside the capital Helsinki, rescue services said.

The injuries were not life threatening, they added.

The children were part of a group of 14 and 15 year olds on a field trip together with their teachers when the bridge collapsed, a Helsinki hospital district physician told a press conference.

"They mainly have limb injuries," chief physician Eero Hirvensalo said.

Police later said they had launched an investigation into the accident that left 26 children and one adult injured with 24 of them needing hospital care.

Police added the temporary bridge had been built from plywood while construction was ongoing in the area.

Finnish media published pictures of at least five people lying on the ground while being attended to by rescue workers.

Prominent figures, including President Sauli Niinisto, expressed their condolences on social media.

"Shocking news about the accident," Niinisto tweeted, adding the focus was now on providing support for those injured.

(Reporting by Essi Lehto, writing by Terje Solsvik, editing by Anna Ringstrom and Christina Fincher)