MORRIS TOWNSHIP, N.J. (AP) — The pilot of a small plane that crashed on a New Jersey highway and killed all five people on board told air traffic controllers he was accumulating ice as he ascended, federal investigators said Wednesday.

The single- engine turboprop plane spiraled out of control, broke apart and crashed in the wooded median of Interstate 287 in Morris Township on Tuesday morning about 15 minutes after it took off from Teterboro Airport en route to Georgia.

Audio recordings made available online Tuesday revealed that controllers cautioned pilot Jeffrey Buckalew and other pilots about icing occurring up to 17,000 feet.

“The pilot confirmed that he was picking up ice,” National Transportation Safety Board investigator in charge Ralph Hicks said at a Wednesday news conference. “How much he was picking up we don’t know, and we may never know.”

The plane was equipped with deicing “boots,” but it wasn’t yet known whether those features were activated, Hicks said.

Killed were the 45-year-old Buckalew, an investment banker with the Greenhill & Co. in New York; his wife, Corrine, and two children; and colleague Rakesh Chawla, 36.

Hicks said Buckalew was licensed to fly single-engine planes and had an instrument rating, meaning he was qualified to fly in weather that requires pilots to use instruments to navigate instead of visually.