Fred Sanders, a spokesman for the Dutch Safety Authority investigation team, also said that the wreckage that has lain in a muddy field since it plunged out of the sky Wednesday one mile short of the runway could be moved Sunday evening.
A Turkish pilots' group claimed that turbulence from a large plane landing at Amsterdam's Schiphol airport shortly before the doomed flight, which was carrying 135 passengers and crew from Istanbul, may have caused the crash.
Turkey Airline Pilots' Association Secretary-General Savas Sen said late Friday that a large Boeing 757 had landed at Schiphol Airport two minutes earlier. Sen said that plane most likely created "wake turbulence" that hampered the Turkish aircraft's landing.
Wake turbulence forms behind an aircraft as it passes through the air.
"All possible causes are (being) investigated and turbulence is known to have caused problems in the past, so you never know," Sanders said.
The investigators on Saturday continued to analyze flight data and cockpit recordings retrieved from the Boeing 737-800's "black boxes" and hope to be able to give a preliminary cause of the crash next week.
In Istanbul, the head of Turkish Airlines' board of directors paid tribute to pilots Hasan Tahsin Arisan, Olgay Ozgur and Murat Sezer and flight attendant Ulvi Murat Eskin at their funerals.
Candan Karlitekin said that, of the 135 people on board, 126 survived due to the pilots' skills.
"It was a miracle but a sad miracle," Karlitekin said in a teary address. "They saved the lives of 126 people and made their families happy, but they died themselves."
Dozens of survivors remained hospitalized Saturday and one was still in critical condition, said Heske Pohlmann, a spokeswoman for Haarlemmermeer municipality.
Boeing Co. said late Friday that three of the American victims were its employees and a fourth Boeing worker remained hospitalized.
Boeing on Friday identified the dead men as Ronald A. Richey of Duvall, Wash.; John Salman of Kent, Wash., and Ricky E. Wilson of Clinton, Wash. A fourth Boeing employee on the flight, Michael T. Hemmer, of Federal Way, Wash., was injured and remained hospitalized, a Boeing statement said.
Boeing Saturday issued a statement on behalf of Hemmer's family that said Hemmer "continues to respond well to treatment in the hospital."
Authorities did not release the identity of the other American and Turk killed.
Pieter van Vollenhoven, head of the Dutch agency investigating the crash, has said that the plane fell almost vertically from the sky, which pointed toward its engines having stopped. He said a reason for that had not yet been established.
Other possible causes under investigation include weather-related factors, insufficient fuel, loss of fuel, navigational errors, pilot fatigue or bird strikes.
Witnesses on the ground said the plane dropped from about 300 feet. It smashed into three pieces as it skidded to a halt in the mud but there was no fire.
The airline also denied reports that the plane, which was built in 2002, had had technical problems in the days before the accident. The plane underwent routine maintenance Feb. 19, and had to delay a flight Feb. 23 - the day before the crash - to replace a faulty caution light.
By Associated Press Writer Toby Sterling; AP Writer Ibrahim Usta in Istanbul contributed to this report