The concrete slab that fell off the O'Donnell Park parking structure this afternoon near Milwaukee's Lakefront claimed the life of a 15-year-old boy, a source told OnMilwaukee.com.

Earlier reports that a 5-year-old child was involved in the accident were erroneous, the source said.

The source, speaking on the condition of anonymity, said that the boy was in a group of four people exiting the structure when the slab fell. Another 15-year-old boy and his mother also were injured, the source said, adding that a man with the group -- the husband and father of the two injured parties -- escaped serious injury.

A second source contacted by OnMilwaukee.com indicated that three of four people involved in the accident were from the East Troy area. Police sources declined to comment on the ages or identities of the victims.

The accident occurred just after 4 p.m., when a 30-foot slab on the east facade of the building plummeted to the pavement across from the Milwaukee Art Museum. The cause of the collapse was not immediately known. Television stations broadcast live video of the scene, which included rescue workers apparently using saws and other heavy equipment to extricate the body of the victim from under the slab.

Eventually, a large blue tarp was used to block the view of onlookers and news choppers.

Within a few hours, officials from OSHA closed the structure, meaning some Downtown workers and visitors will be unable to retrieve cars parked in the structure for at least a day and possibly longer.

After the accident, Lincoln Memorial Drive and several other streets in the area were closed to make room for emergency vehicles, which caused huge traffic backups near the Summerfest grounds and the museum.

A Milwaukee County official estimated that O'Donnell Park opened in the early 1990s and said that the structure covers seven acres of land and features 1,250 parking spaces.

Although it was plagued by some problems during construction and criticized in many circles as a waste of taxpayer money, the structure has operated without incident for the past 15 years. Many residents didn't think about it until last winter, when a group of bike polo players were cited for trespassing for playing their sport in the facility during off-hours.

In a statement Thursday, Milwaukee County Board Chairman Lee Holloway criticized the county's recent penchant for deferring maintenance and asked for a review of all county facilities.

"Earlier this year, stone chunks fell off of the Milwaukee County Courthouse," Holloway said. "We are also dealing with numerous structural problems at the Mental Health Complex. Now, today, we are dealing with a terrible tragedy."

Milwaukee County Executive Scott Walker and Mayor Tom Barrett, who are both running for governor, issued statements expressing condolences to the victims and their families.

Sources close to the campaigns of both men said Thursday night that the O'Donnell Park accident could become an issue in the election. Earlier this year, Walker criticized Barrett and Governor Jim Doyle when bridges near the Zoo Interchange needed replacing.