Mayor Cherelle Parker said five people are still hospitalized following a fatal medical jet crash in Northeast Philadelphia, three of whom are in critical condition.

Investigators have not been able to locate the aircraft's black box yet, which could provide clues into the cause of the crash.

The Learjet, carrying a pediatric patient and five others, crashed on Friday, killing all on board. On the ground, one person was killed and at least 19 others were injured, officials said.