Five of the 22 people injured on the ground when the Learjet 55 crashed near the Roosevelt Mall on Friday are in hospital, according to Philadelphia Mayor Cherelle Parker.

Three of those are in critical condition, she said.

None of the six people on board the medical jet survived. An additional person on the ground was also killed – bringing the death toll to seven, officials said.

Philadelphia Police have been working to reopen roads around the crash site.

The outer lanes of the Roosevelt Boulevard have been reopened in both directions, according to a statement from the Philadelphia mayor’s office on Sunday.

Cottman Avenue remains closed due to the National Transportation Safety Board’s active investigation into the cause of the accident.

Delays are expected on surrounding roads, the statement read.

A family member of one of the 22 people injured – along with seven killed – during Friday’s plane crash has spoken out.

Dominque Fletcher was in the car with her partner and his son while driving the Roosevelt Mall on Cottman Avenue when the Learjet 55 aircraft crashed in a fireball shortly after taking off on Friday evening.

The victim’s 33-year-old cousin, Shentelle Fletcher, has revealed the extent of the woman’s injuries.

“She is in a medically induced coma,” she told NBC10 on Sunday.

“Seventy percent of her body is burnt. She’s responding well to medication. She has surgery scheduled for today.”

The black box has been recovered from the medical jet that crashed in Northeast Philadelphia on Friday, killing all six passengers on board.

The device was found eight feet underground at the crash site near the Roosevelt Mall, the National Transportation Safety Board said on Sunday evening.

The black box – also known as a cockpit voice recorder – remained in “decent shape,” sources told WPVI. The plane’s enhanced ground proximity warning system, containing flight data, was also recovered, the NTSB said.

Former NTSB investigator Dr. Alan Diehl tells Fox News the search for answers in the Philadelphia plane crash may prove difficult due to “fragmentation.”

“The cockpit voice recorder will be critical,” Diehl said.

“[The investigation] will be very difficult if that voice recorder is not intact, or they can’t find it,” he added, noting it “should have” survived the impact but that the violent nature of the crash could make the search difficult.

NTSB Chairwoman Jennifer Homendy stressed it is not unusual for the agency to be investigating two major accidents at once. “We are a highly-skilled agency,” she said during a news briefing in Philadelphia Saturday.

The NTSB has 436 employees spanning across all modes of transportation. The agency has two separate teams of investigators probing crashes in Philadelphia and Washington D.C. at the respective scenes.

Here’s everything we know so far about the Philadelphia plane crash, from The Independent’s Mike Bedigan and Namita Singh: