TORONTO -- There is nothing at this time to suggest criminal activity was involved in a mysterious underground chamber found near a Pan Am Games venue, but the intentions of whoever built it remain unknown, police said Tuesday as they appealed for help in their investigation.

The underground bunker, discovered in January by a conservation officer in a densely wooded area, is located 25 metres from the fence of the Rexall Centre, which is to host tennis events for the summer's Pan Am Games.

But while police are still trying to figure out who built the chamber and why, they emphasized that the structure wasn't currently thought to pose a public safety threat.

"I don't have any evidence that suggests criminality at this point," said Deputy Chief Mark Saunders. "But bear in mind I don't have the intent behind this at this point, that could change. I'm open to anything right now."

Saunders called the discovery of the bunker "not your every day find," and said police would continue to investigate until they discovered who built it.

"In light of today's present circumstances, anything that we don't have an answer to, we want to fully explore, we want to get the answers and if it compromises public safety, we have a concern," he said. "So until we get what the intent is behind this, we're going to continue to investigate."

The police probe so far has determined that the chamber was used at some point during the winter.

Those responsible for building it clearly had some level of expertise in ensuring its structural integrity, Saunders said.

"Whoever decided to build this took quite a bit of time," he added.

Police found plywood wall supports, a generator, moisture resistant light bulbs and a sump pump in the chamber.

They also found a rosary with a Remembrance Day poppy nailed on to a wall in the chamber and food and beverage containers.

The chamber measures two metres in height, 71 centimetres in width and 10 metres in length.