Hundreds of residents without power — many of them elderly — were evacuated from high-rises in a densely populated area of the city's South Side Tuesday morning as temperatures were forecast to climb into the 90s for the fifth straight day.

About 350 of the most fragile evacuees were taken to several Chicago hotels, officials said. Another 600 were taken to the nearby McCormick Place convention center, and that number was expected to rise, said Chicago Fire Department spokesman Larry Langford.

Nine people were transported to hospitals with heat-related illnesses, but none were in serious Officials said up to 20,000 people lost electricity in an outage that began at about 7:30 p.m. condition, Langford said Monday. ComEd crews hoped to have power restored by Tuesday afternoon

As firefighters rounded up residents before sunrise, apartment dwellers described the scene as chaotic.

"It's a mess," said Lenora Stinson, 47. "It's a big mess. Everybody's panicking — they don't know where they're going."

But Stinson, who was in an 11th floor apartment when the power went out, said firefighters were doing a good job of getting people out of the building, especially the elderly.

Artra M. Thomas, 38, disagreed, saying she had to evacuate herself.

"I'm asthmatic (but) I was able to fend for myself," she said, adding that she felt someone should have come to check on her and others with health conditions.

ComEd spokesman Fidel Marquez said the outage was caused by a failure in an underground cable and that the weather may not have been a factor.

"Failures of this type can happen in any kind of weather," he said.

ComEd spokeswoman Judy Rader said at its peak, the outage affected 3,500 customers. That translates to up to 20,000 people.