Virginia Beach Fire Department Battalion Chief Tim Riley stressed that some residents had still not been accounted for, though none had officially been reported missing so far.
Part of the jet's wreckage lay on the grass behind some buildings after emergency teams doused the area with foam to tamp down the blaze.
Authorities were still scouring through the charred wreckage of about 40 apartment units after the massive blaze ignited by the crash blew off the roofs of buildings, charring and burning top floors.
The two crew members ejected safely from the jet which hit a populated area in the eastern coastal tourist resort of Virginia Beach, officials said.
US Navy Captain Mark Weisgerber blamed a "catastrophic mechanical malfunction" for the crash. Governor Bob McDonnell told CNN officials were hoping to confirm a "Good Friday miracle," with no loss of life.
The specifics of the mishap were still unknown, Weisgerber said, but added that it resulted in the "forced ejection" of the crew -- a local student pilot in the front seat and an experienced instructor in the back.
The city's mayor William Sessoms told CNN that nine people had been injured including the pilots.
Sentara Healthcare said all but one of the seven people taken to hospital with non life-threatening injuries had been released. Only one of the pilots remained at Sentara Virginia Beach General Hospital.
"The crew is doing well. They suffered some minor injuries and the latest report is that they're up and about and both coherent and doing well," Weisgerber told reporters.
McDonnell hailed the pilots, saying their last-minute ejection and the quick response from emergency workers on the ground had likely "saved a lot of lives."
Witnesses said the plane came down suddenly and that the spilling of jet fuel may have exacerbated the flames.
"The buildings were starting to collapse," Zack Zapatero told CNN.
"I did not see anyone running out and I was told that there's a bunch of senior citizens that live in those buildings which worries me a lot.
"It was just unbelievable. Law enforcement was really quick to get on the scene. But the amount of jet fuel that you could just smell on the ground, it didn't seem right," he said.
Another witness, Jon Swain, described how the plane smashed into the apartment block.
"There were flames coming out of its engine at the back, which I just thought was afterburn or whatever... but the plane got lower and lower. I saw one pilot eject," he told MSNBC.
"It hit it dead center. And yeah, it's pretty traumatic. There were a few people running from the building."
Another witness, Joanna Highet, also said the plane was very low and had disappeared out of her line of sight behind some trees.
"Initially we heard nothing, and then when the smoke started after about 15, 20, 30 seconds we heard an explosion," she told CNN.
"We drove back and saw lots of black smoke and the apartment complex on fire from both ends."
The F-18 jet was assigned to Naval Air Station Oceana. The crash took place in an area known as Hampton Roads that is home to many US military facilities, including the world's largest naval base, Naval Station Norfolk.
Oceana, which is a vast complex with more than seven miles (10 kilometers) of runways, is manned by 14,600 military personnel and home to 19 fighter squadrons.
The Navy said in a statement that it was "continuing to coordinate with local authorities, and the cause of the accident is under investigation."