A third-floor porch packed with dozens of friends suddenly collapsed yesterday, killing 12 people as it pancaked onto porches below. As many as 45 others were injured in the fall, some critically.

　　Chicago Police said as many as 50 people, most of them in their early 20s, may have been standing on the wooden porch when it gave way, and that there may have been beer kegs and people dancing there, as well.

　　"There was chaos," said Chicago Fire Commissioner James Joyce. "There were people screaming and crying in the alley."

　　Eleven people were dead at the scene, and others were trapped in a basement stairwell, authorities said. The Cook County Medical Examiner's office confirmed that a 12th person was dead on arrival at a hospital.

　　"It was simply a case of too many people in a small space," Joyce said.

　　Cortez Trotter, Chicago's Emergency Management director, said 45 people were injured when the floor of the porch, attached to the back of an apartment building collapsed just after midnight.

　　Most of the people at the party were friends, many of them graduates of New Trier High School in Chicago's northern suburbs, said Fina Cannon. She had been in the kitchen, looking out at the porch when it gave way.

　　"All of a sudden I saw all these heads going down," Cannon said. "The floor just dropped out from underneath them. They all went down in unison."

　　A lot of people were on the third-floor porch at the time, and others on the second-floor porch below it, Cannon told Chicago television station CLTV.