City officials will have to wait at least another day to learn the identity of the mysterious, smelly sludge that was pouring out of a discharge pipe into the Niagara River.

The slop, which was spilling out of what’s believed to be a city stormwater drain pipe just north of the Rainbow Bridge, was discovered during a Sunday rescue of a 27-year-old London, Ont. man who fell about nine metres down the side of the Niagara gorge.

Fire fighters with the Niagara Falls Fire Department were concerned, although not necessarily worried, about their exposure to the unknown substance during their rescue of the injured man, said platoon chief Doug Mann.

“We deal with so many different environmental hazards and situations that anytime we can eliminate a problem, we like to do that,” Mann said.

Mann also said firefighters want to know what they were dealing with when they rescued the London man.

“Until we determine what it is, it’s treated as a possible health hazard of an unknown nature,” Mann said.

Kent Schachowskoj, the city’s acting director of municipal works, said that officials with the city, Niagara Region, Niagara Falls Fire, and the Ministry of the Environment were at the scene on Monday to investigate.

“We’ve taken some samples from the discharge pipe,” Schachowskoj said. “They have been sent off to the lab but we won’t have results for at least a day — maybe at the end of the day tomorrow, but more than likely it might be Wednesday before we have any results.”

Mann said three men entered the gorge early Sunday morning. They climbed to the top of the pipe, when one of the men slipped and slid about nine metres to the bottom, suffering head trauma and a serious leg fracture when he landed.

Fire crews were dispatched to the scene, where they found the injured man covered in the slop before being brought up by rescue basket to street level.

Charges under the Niagara Parks Act of Ontario were pending.

Schachowskoj said that on Monday, the sludge didn’t appear to be flowing from the pipe anymore and that it was possible the spillover on Sunday could’ve been overflow caused by last week’s rain. The samples taken Monday resembled plain water.

“The samples seem to be generally clear,” Schachowskoj said. “It looked like rainwater or normal drinking water.”

He said the initial speculation that the sludge could’ve been raw sewage was based on its awful aroma.

“That was just based on smell,” Schachowskoj said. “It smelled bad but in terms of what is actually in it, hopefully the testing on the samples that we took this afternoon will let us know what we’re dealing with here.”