A small medical transport plane crashed into several buildings in north-east Philadelphia on Friday evening, killing all six people on board and at least one other person on the ground, according to the city’s mayor.

Foreign media reported that the jet was on a medical transport trip, carrying a child patient and her mother, along with four crew. All six aboard were Mexican nationals. Another person who was in a car on the ground at the time of the crash was killed, Philadelphia Mayor Cherelle Parker said. Nineteen others were injured, though the city leader said that number could change.

Speaking at the same press conference on Saturday, Philadelphia city managing director Adam Thiel said it would probably be “days or more” until officials are able to “definitively answer the question about the number of folks who perished in this tragedy and the outcome of those who were injured”. He added that there remain “a lot of unknowns about who was where on the streets of this neighbourhood last night at the time of impact”.

Flight logs show the plane was in the air “for only a minute” before it crashed, Mayor Parker said in an earlier statement. Pennsylvania Gov Josh Shapiro called it an “awful aviation disaster”. Videos of the incident show the plane coming down quickly and sparking a huge fireball.

Mexican President Claudia Sheinbaum confirmed all six people on board were from that country. “I mourn the passing of six Mexicans in the aviation accident in Philadelphia, United States,” she said in a statement translated from Spanish.

The girl on the plane, from Tijuana, Mexico, had received an unspecified treatment at Shriners Children’s Philadelphia, said hospital spokesman Mel Bower. Bower said the girl’s treatment had ended and she was on her way home, and that there had been “a send-off” at the hospital for her earlier on Friday. He added that two doctors on the plane were from the Jet Air Rescue Air Ambulance.