TOWN OF BELOIT, Wis. -- Rock County authorities are investigating a Wednesday night fire that left two Town of Beloit residents dead.

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The blaze apparently broke out at about 11:20 p.m. Wednesday at a residence on Dewey Avenue, just north of the city of Beloit. Firefighters arrived to find heavy fire and smoke damage to the home, WISC-TV reported.

Authorities said that one of the victims was pronounced dead at the scene while the other died at Beloit Memorial Hospital. The Rock County Coroners Office said Thursday afternoon that both victims died of carbon monoxide poisoning related to the fire.

Nearby residents on Thursday were mourning the couple that lived on the corner.

"We just knew there was a fire, and we didn't know who was in or who had gotten out," said Susan Heyerdahl, whose brother died in the blaze.

Authorities identified the victims as Paul and Carol Brom, both 70.

Firefighters are trying to determine how the fire started.

Neighbors said they saw flames shooting out of the house during the blaze Wednesday night.

"Flames were coming out of the two windows on this side, and they were coming out for quite some time. I mean, it took them a little while to get water going there," said Al Barker, who lives near the victims' home.

Carol Brom was removed from the home and transported to Beloit Memorial Hospital.

"They did get her to the hospital, but she didn't make it. And they couldn't get my brother out," Heyerdahl said. "There was too much smoke. They finally got him out about 3 o'clock. But he didn't make it either."

Firefighters said they did everything they could, but the fire had spread throughout the house from the basement, making a rescue impossible.

"The heat, the flash-over conditions -- the heat got so extreme that our guys, even in gear, had to bail out of the residence. After finding the first victim, they couldn't see inside the residence," said Lt. Allen Cass, of the Town of Beloit Fire Department.

On Thursday night, family members said they are waiting for answers.

"Everybody liked them. They had a lot of friends. I don't know how it started," Heyerdahl said.

"We'll have to take care of each other -- that's all. We'll have to take care of each other," said Julie Burns, niece of the fire victims.

The state crime lab is assisting the Town of Beloit Fire Department in the investigation, although officials said they don't suspect foul play.

Neighbors said they believe the community will reach out to the Broms' families to offer any support they can.