CHICAGO, June 29: A balcony crammed with party-goers collapsed early on Sunday, sending bodies and splintered wood plummeting three stories into a tangled mass that killed 12 and injured dozens, authorities said.

“There was chaos. People were screaming and crying in the alley,” Chicago Fire Commissioner James Joyce said.

Some witnesses reported hearing a creaking sound as the overloaded top floor of the wooden structure gave way, crushing people on lower floors and trapping them at the basement level. Others were left dangling from the ruined structure.

“It just happened. I was in shock,” said one woman leaving a hospital who gave her name as Angie Desai. She said there was no warning before she and others dropped from the top floor and was dragged to safety by a friend.

Other guests at the party, which appeared to involve more than one apartment in the six-unit building, described the swiftness of the collapse as the heads of their friends dropped from sight when the top deck gave way.

The accident occurred behind an apartment building in the upscale North Side neighbourhood near DePaul University, a popular area dotted with numerous nightclubs and bars.

Survivors tried to pull friends from the mass of bodies and shattered wood and neighbours used torn bedsheets and ice from a nearby tavern to pack wounds until paramedics arrived.

Fire Department rescuers used chain saws to cut through to victims trapped at the basement level.

“As they got deeper into the pile of humanity the injuries were more serious,” Joyce said.

Many of the estimated 45 injured suffered cuts or broken bones, with 10 listed in critical condition.

One woman arrived at the hospital “dead on arrival” but was resuscitated, Dr. John Kirby told reporters.

Witnesses estimated 70 people were on the decks and stairways when the top floor gave way, Joyce said. “It appears to be a case of too many people in a small space,” he said.

One unidentified man told local radio, “There were bodies and people everywhere. It was mayhem.”

The skeletal railings of the structure, which authorities said appeared to be fairly new, were still standing hours later minus the missing floorboards and staircases.

The Cook County Medical Examiner’s office said it had received 12 bodies from the accident, both men and women. Most of the dead appeared to have been on the second floor.

“The third floor collapsed, taking the second and first floors with it and trapping people underneath,” city Emergency Management Director Cortez Kennedy said.

Wooden balconies are a common sight at the rear of Chicago apartment buildings, and collapses can occur as the crudely constructed structures age, sometimes with deadly effect.

The city’s building department recently sent out a warning to inspect the structures with the arrival of summer. “Porches are not designed for large parties,” the press release said.

“Common sense should prevail at some point,” Kennedy said when asked if there were official capacity guidelines.—Reuters