Toronto police are baffled over a "sophisticated" mystery tunnel uncovered last month near one of the venues for the Pan American Games, a sporting event that kicks off this summer.

Cops are so perplexed over who would have dug out a 33-foot-long underground pathway that on Tuesday they asked for the public's help. "The individuals responsible for building it clearly had some level of expertise in ensuring its structural integrity," Toronto Deputy Chief Mark Saunders said at a news conference.

No one was inside the reinforced tunnel when a conservation officer found its entrance near a pile of dirt in the city's Black Creek Parkland. But there were signs of life nine feet down: moisture resistant light bulbs, a pulley system to move dirt, a gas container, work gloves, a wheel barrow and food waste. Inside a connecting hole was a gas generator. Officials also retrieved a rosary and a Remembrance Day poppy nailed to a wall.

The tunnel — at a height of 6-foot-4 and width of 2-foot-10 — would have opened on the forest side of a chain-link fence if it had been completed. Toronto police found no immediate evidence that the tunnel is linked to terrorism or drug production, according to reports.

Saunders said there's generally "no criminal offense for digging a hole," although it could lead to criminal charges depending on the intent of the diggers. Security, he added, will be "robust" in the area for the Pan Am Games.

SOCIAL

Take a look at evidence yourself @TorontoPolice don't know who/why tunnel built http://t.co/KFXEhenj1x pic.twitter.com/tk0xvNL2z5 — Kevin Masterman (@tpspix) February 24, 2015

PHOTO GALLERY of @TorontoPolice Tunnel Find http://t.co/AQXmcQIcx1 in Black Creek parkland pic.twitter.com/4yvEpo6VoO — Kevin Masterman (@tpspix) February 24, 2015

— Erik Ortiz