Ottawa (AFP) - Toronto police said Monday they now know who dug a tunnel near a major sporting venue in the city -- a mystery that has been a source of widespread speculation and conspiracy theories.

In a statement, police said two young men stepped forward to acknowledge responsibility after authorities made a public plea for help to determine its purpose.

"The two men told investigators they built the tunnel for personal reasons," police said.

They added that their account has been verified, and that authorities "are satisfied there was neither criminal intent nor any threat to the people or city of Toronto."

The tunnel, which also is situated near Toronto's York University, was discovered by a wildlife official walking through woods. He spotted a piece of corrugated metal on the ground, lifted it up and found a passageway.

It was more than six feet (1.8 meters) high, almost three feet (0.9 meters) wide and about 33 feet (10 meters) long, and was hidden in a densely wooded area of the city, "well off the beaten path," deputy police chief Mark Saunders told a press conference last week.

Had it continued, the tunnel would have exited on the other side of a hill overlooking nearby tennis courts and a sports facility that will host the Pan American Games in July.

Its discovery provoked widespread speculation about who built it and why.

National security officials were alerted, but suggestions the tunnel posed a threat were quickly dismissed. Police also said it was not a drug lab.

Online sleuths and media suggested it could be a survivalist's fallout shelter, a prank, or a niche home in Toronto's red hot condo market.

American horror writer Stephen King weighed in that it was likely a wormhole built by aliens.

Before it was filled in, the second in command of Canada's largest city police force described the interior of the tunnel as humid and warm.

The walls were lined with plywood and reinforced with wood framing. It was lit by an electric generator and a sump pump was used to keep it dry.

Police also found a bucket and pulleys and a wheelbarrow likely used in the dig.

As well, a rosary with a poppy attached was nailed to an inside wall, and discarded food and beverage containers point to someone having used the tunnel over the winter, Saunders said.