6:15 p.m. Sunday Update: Battalion Chief Joe Vitale said that no fatalities occurred during the apartment building fire. There is not yet an official cause of the fire as the investigation is continuing.

Update: A news release from Battalion Chief Joe Hoffman states the origin of the fire was a mattress in the 30-unit apartment building.

"The resident of the apartment of origin, stated that he was giving his kids a bath when he smelled smoke and discovered a fire in his bedroom and his entire mattress on fire," the release states. "He immediately returned to get his kids out of the bath and exit the structure while pulling the buildings fire alarm as he exited."

The apartment's resident was treated for smoke inhalation and was released from the hospital, the release states.

The Waukesha Fire Department rescued six people from the second and third floors when a fire ripped through a large apartment building at 212 W. North St. Saturday evening.

"Our crews focused on the life-safety aspect and removed those people from the building using both interior modes and outside ladders," Assistant Fire Chief of Operations Jesse Alba said. "After that they initiated fire attack and have been working on that ever since."

There are still people unaccounted for but because the fire occurred at 4:15 p.m. Saturday, Alba said he is hopeful the people were not in the building.

"There are a lot of people out and about on a Saturday afternoon and the Packers game, so there certainly could be people out and about in the community," Alba said. "We are going to initiate a secondary search of those apartments that they believe people are missing from.

"Their neighbors have been very helpful to say whether people lived in those units and whether or not they were home or not at the time of the fire or if they see them in the sanctuary we provided for them at the Salvation Army and a community bus."

There were no injuries that were reported by 7:45 p.m., said Alba, whose turnout gear was covered in ice. Alba's helmet had icicles hanging from it.

"The people that we removed, all of them were fine," Alba said. "I haven’t heard that they have received treatment at all."

Ice covered the street and three firefighters slipped but were not injured. Alba said the city's Department of Public Works was helping by spreading salt in the area as ice was developing.

Although the fire was two blocks from Fire Station No. 1 and the department responded in two minutes, the apartment building is unstable, Alba said.

When the firefighters arrived, there already was a large volume of fire in two apartments. The fire reached the attic, spread through the second and third floors and extended through the entire building, Alba said.

The fire department does not yet have a cause of the fire or determined its origin.

"Two apartments are very rare," Alba said. "Considering our proximity and a two-minute response time, I can’t explain it, so that will be part of the investigation process."

The people who were displaced by the fire are currently receiving shelter at the Salvation Army and in Waukesha Metro Transit buses.

Gene Pawlak lives down the street from the apartment building, and when he saw the fire develop, he said he realized the building was gone.

"I heard all the fire trucks come out … I looked out and, wow, flames are flying big time," Pawlak said. "I seen them coming out the front. They were at least 20, 30 feet up in the air."

Brent Rectenwald said he was working on a snow removal job near Buchner Park when his friend heard the call on a police scanner. Rectenwald looked up in the sky and could see the fire from the park, which is at least a mile away.

"You could see it and it was orange," he said. "As we came, it was pretty good-sized flames."