Calgary's fire department shut down a northeast street to clean up what was initially believed to be biological waste.

Fire crews shut down westbound 80th Avenue N.E. between Taradale Drive and Saddlefield Drive around 3:45 p.m. Tuesday so the city's roads department could deal with what was initially believed to be hazardous material. Police were also on scene.

The fire department's spokesperson said the road was blanketed in "some sort of waste material, like poo."

It was unknown how the waste got there.

But, it wasn't long before the stinky mystery was solved.

"Preliminary indicators led firefighters to believe that it was poop, but when the party responsible for the spill returned to the scene they indicated that it was actually 'pond-scum' that had spilled on the road," the fire department said shortly after 7 p.m.

A construction company owned up to the spill and was responsible for cleanup.

The road was cleaned and reopened to traffic by 5:20 p.m.