By Jim Melwert, Mike Dunn and Jenn Bernstein

READ MORE: Hyram Hill, Son Of Philadelphia Police Officer, Killed In Targeted Shooting In North Philly, Sources Say

PHILADELPHIA (CBS) — During a press conference on Tuesday afternoon, Mayor Nutter referenced several rumors connected to a row home explosion in South Philadelphia on Monday, calling one “pure speculation.”

An official at the scene Monday said that the worker who was burned in the basement of 428 Daly Street was having issues with a water heater as he renovated the unoccupied row home. Earlier today, Councilman Mark Squilla visited the site and told reporters the contractor lit a cigarette.

“He supposedly went in the building, tried to do it, couldn’t get it to work, went out, came back in. Sometime during that process he lit a cigarette and when that happened the house exploded,” Squilla said.

But on Tuesday, Mayor Nutter said that those rumors were “pure speculation at this point,” and that the Fire Marshal is still investigating the incident.

READ MORE: Flyers Tie Franchise Record With 12th Straight Loss

Furthermore, Mayor Nutter said they have no firm evidence of a gas leak at the site of the explosion. He says work on the hot water heater was completed and certified by an L&I inspector the previous Friday. And the Mayor says it appears that the contractor at the site on Monday was a flooring worker.

“It is our best understanding that the individual who was injured was doing other work inside the house, possible described as a tile person. The hot water heater as best we understand, at an inspection on Friday, had already been installed,” Nutter said.

The contractor remains hospitalized and investigators cannot yet question him.

Eight people, including three children, were injured during the explosion. One person remains in critical condition at Temple University Hospital.

MORE NEWS: Gino's Ristorante & Pizzeria Reopens Amid Hepatitis A Investigation That's Linked To 10 Cases, 3 Deaths