NASHVILLE (AP) — The pilot of a single-engine plane that crashed near downtown Nashville told air traffic controllers he could see the runway they were clearing for an emergency landing. But he said he couldn't reach it.

"I'm going to be landing -- I don't know where!" the pilot said before the plane crashed alongside Interstate 40, killing all five people aboard.

The pilot had another adult and three children on board, National Transportation Safety Board investigator Aaron McCarter said at a Tuesday news conference. He said the five are Canadian citizens, and the agency is working with the Canadian government to determine their identities.

He said it is too early to know what caused the crash. Investigators do not yet know the pilot's qualifications or how many flight hours he had, but his experience is one of the things they will be investigating.

The pilot radioed air traffic controllers at around 7:40 p.m. Monday reporting that his engine had shut down. He said he had overflown John C. Tune airport, just west of downtown, at 2,500 feet and had circled around in an attempt to land, according to a recording of their radio transmissions.

They cleared runway two at the airport, and urged him to glide the plane down. But the plane had already descended to 1,600 feet (488 meters) by then, he said.

"I'm too far away. I'm not going to make it," he said.

That was the last they heard from the plane, which dropped off radar as it lost altitude.

The plane crashed as Matthew Wiser was driving on the interstate, and he posted a photo of the fiery wreckage on social media.

"I saw an airplane essentially crash out of the sky, fall out of the sky, and hit the ground at around a 45 degree angle," Wiser said in a phone interview. "When it hit the ground, there was a 30 to 40 foot explosion of fire. And all of the traffic on the interstate stopped and kind of processed what they saw."

Air traffic controllers then directed a local helicopter crew to survey the approach to the airport in search of the plane, while keeping other aircraft out of the emergency area. Within minutes, a flood of emergency vehicles were speeding to the scene, Wiser said.

They discovered that the plane burst into flames in the grass, just off the highway and behind a Costco on the city's westside, about 3 miles (4.8 kilometers) south of the general aviation airport.

"It appears that everyone on board perished," Metro Nashville Police Department spokesman Don Aaron said.

The plane referred to in the radio recordings was a Piper PA-32R, made in 1978 and based in Ontario, according to Canada's civil aircraft registry. It took off from the Milton, Ontario, area Tuesday afternoon, according to FlightAware, which tracks flight activity.

There were no injuries to drivers on the interstate, Nashville Fire Department spokesperson Kendra Loney said. Authorities said no vehicles or buildings on the ground were damaged.

The Federal Aviation Administration and National Transportation Safety Board are investigating. McCarter said they packed up the wreckage for transport to a facility in Springfield, Tennessee, where the plane will be reassembled.

Investigators do not know why the pilot decided to circle the airport prior to the crash, he said. He mentioned that the plane's approach was perpendicular to the interstate when it hit the ground.

The NTSB will have a preliminary report out in about 10 days. The full report will take about 9 months.

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Associated Press contributors include Sarah Brumfield in Silver Spring, Maryland, and Julie Walker in New York.