The last Aviation Herald update adds some more indications that the first landing attempt was made with landing gear up:
On May 24th 2020 Pakistan's media quote a CAA official speaking on condition of anonymity that the aircraft made two attempts to land. During the first approach it appears the landing gear was still retracted when the aircraft neared the runway, the pilot had not indicated any anomaly or emergency, emergency services thus did not respond and did not foam the runway as would be done in case of a gear malfunction. The marks on the runway between 4500 feet and 7000 feet down the runway suggest the engines made contact with the runway surface, it is possible that the engines were damaged during that contact with the runway surface leading even to possibly fire.
On May 24th 2020 a spokesman of the airline said, the landing gear had not been (partially or fully) lowered prior to the first touch down. The crew did not call out the standard operating procedures for an anomaly and no emergency was declared. Most likely the crew was not mentally prepared for a belly landing and went around when they realized the engines were scraping the runway.
Crash: PIA A320 at Karachi on May 22nd 2020, impacted residential area during final approach, both engines failed as result of a gear up touchdown