Amsterdam ? Engine trouble may have caused the Turkish Airlines crash that killed nine people in the Netherlands, the head of the agency investigating the accident said Thursday. Other officials identified the dead as five Turks and four Americans.

Flight TK1951 from Istanbul crashed about one mile short of the runway at Amsterdam’s Schiphol Airport on Wednesday morning, smashing into three pieces and spraying luggage and debris across a field. It was carrying 135 passengers and crew.

Chief investigator Pieter van Vollenhoven said, in remarks quoted by Dutch state television NOS, that the Boeing 737-800 had fallen almost directly from the sky, which pointed toward the plane’s engines having stopped. He said a reason for that had not yet been established.

Spokeswoman Sandra Groenendal of the Dutch Safety Authority confirmed his remarks and added that engine failure was still only “one of the possible scenarios” for the crash.

Van Vollenhoven said an analysis of the plane’s flight data recorders in Paris could be completed as early as today, but his agency would probably not make a preliminary finding until next week.

“We hope to have a firmer grip as soon as possible,” he said, adding that the information retrieved from the recorders was of high quality.

Survivors say engine noise seemed to stop, the plane shuddered and then simply fell out of the sky tail-first. Witnesses on the ground said the plane dropped from about 300 feet.

Haarlemmermeer mayor Theo Weterings said five Turks and four Americans were killed in the crash. He said that the names of the victims would not be released until the bodies have been formally identified.

Haarlemmermeer also said Thursday that investigators now say 135 passengers and crew were on the flight, not 134 as previously believed, which was one reason it had taken so long to account for the dead.

Turkish Airlines chief Temel Kotil said the captain, Hasan Tahsin Arisan, was an experienced former air force pilot. Turkish officials said the plane was built in 2002.

Turkish Airlines issued a statement Thursday denying reports that the plane had had technical problems in the days before the accident.