The NTSB said a preliminary report, to be released within a month, will contain "factual information" gathered in the investigation.

NTSB investigators found the Learjet 55's cockpit voice recorder Sunday. The agency said it was 8 feet down at the site of initial impact. The death toll is 7, with 22 injured.

There were also casualties on the ground. Philadelphia Mayor Cherelle Parker said one person who was in a car was killed and 19 others were injured. The jet was transporting a child who had just completed treatment at Shriners Children's hospital, her mother and four crew members.