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Julio Cortez, AP Photo
Ralph Hicks, investigator in charge with the National Transportation Safety Board, walks away after a news conference about the developments in the collection of debris of a plane that crashed on the highway, Wednesday, Dec. 21, 2011, in Morris Township, N.J. The high-performance Socata TBM-700 turboprop spun out of control and crashed, killing all five people aboard and narrowly avoiding dozens of cars and trucks on Highway 287 on Dec. 20. Federal investigators are searching for debris, which were scattered over at least a half-mile, with one section found lodged in a tree a quarter-mile away.

MORRIS TOWNSHIP, N.J. — 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 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.

Salvage crews on Wednesday finished removing the wreckage from an area around Interstate 287, a busy corridor that rings the suburbs west of New York City. Hicks said the largest pieces removed were the main cabin and a 10-foot section of wing. The debris was strewn across the highway, median and surrounding terrain Tuesday, forcing the road to be closed for several hours.

The NTSB will reassemble the plane at a warehouse in Delaware as part of an investigation that it said could take up to a year. A preliminary factual report is expected to be released next week.

Hicks said investigators were still hoping to find some type of memory device, such as a GPS that could yield more information. The Socata TBM-700 was not required to carry a black box, as commercial jetliners are. The plane's maintenance records were being retrieved from a facility in Groton, Conn., he said.

The plane disappeared from radar at 17,500 feet, about 14 minutes into its flight from Teterboro to DeKalb-Peachtree Airport near Atlanta. Reports of severe icing at 14,000 feet had been received by air traffic controllers.

Ice can form on airplanes when temperatures are near freezing and there is visible moisture, such as clouds or rain. The ice adds weight to an aircraft, and rough accumulations known as rime interrupt the flow of air over wings. In extreme cases, a plane can lose so much lift that it falls out of the sky.

Witnesses described an out-of-control descent.

Will Keyser, who works in maintenance at the Spring Brook Country Club in Morristown, is used to hearing small planes fly over en route to nearby Morristown Memorial Airport. He was near the 13th hole Tuesday when he heard a loud plane overhead.

He said the plane pitched back and forth, and for a moment he thought it was a stunt pilot.

"It was kind of rolling and making circles — 'cause I've seen air shows before — so I thought: 'Oh, OK;' but then he finally did a nosedive and we realized that was completely wrong."