“There's nothing in the river for us to find in terms of an airplane or helicopter or something that went down (Monday) night,” Ottawa police Const. Alain Boucher said Tuesday afternoon.

“We're still looking into what could have caused this. There's a number of reasons this could have happened. We'll be looking into that in the next couple of days.”

Problem was, there was no physical evidence pointing to a plane wreck: No debris, no oil slick and no indication from airspace authorities that something fell off the radar. There was also no report of a missing aircraft.

Still, searchers launched their boats on Tuesday morning looking for clues that could confirm witness accounts.

They found a few objects in the water, but nothing significant until around 1:30 p.m., when sonar discovered something bulky more than nine metres below the surface.

An underwater camera couldn't reach it and searchers called off the mission not knowing exactly what the object was.

Een ufo in de meest letterlijke zin van het woord dus, niemand weet wat het was en waar het is.