A fire that damaged part of a wooden bridge in a Nanaimo park was intentionally set, according to investigators.

The walking bridge near the duck pond in Bowen Park was set aflame in the early hours of June 3.

A dog walker spotted the fire at around 6 a.m. and jumped into action before it could spread to the surrounding tinder-dry forest.

The 58-year-old Nanaimo man ran to his nearby home, got a fire extinguisher and returned to douse the flames.

Fire crews then arrived and put out a smouldering wooden post.

"This was an extremely selfish deliberate act that could have caused significant damage to not only the bridge but to the surrounding forest," said Nanaimo RCMP spokesman Const. Gary O'Brien.

While the bridge was spared from a worse fate, it remains closed to the public due to its age and unsafe condition.

Anyone who has information on the suspicious fire is asked to call police at 250-754-2345 or Crime Stoppers at 1-800-222-8477.