Amsterdam  - Two employees of the US plane-builder Boeing were among the nine dead in Wednesday's plane crash outside Amsterdam's Schiphol airport, the company confirmed early Friday.

A third employee of the firm, who had been on board the Turkish Boeing 737-800 that crashed on approach to the airport, was injured and remains in hospital, the Seattle-based concern said in a statement.

Boeing is awaiting information from the crash investigation about what caused the accident, which came at the end of the scheduled morning flight from Istanbul when the aircraft came down suddenly short of the airport runway.

Investigators of the Dutch Safety Board, which investigates all major accidents in the Netherlands, are at the crash scene and the plane was to remain at the site for further investigations expected to last at least until Sunday.

The board said it would publish details of the analysis it made of flight data recorder and the cockpit voice recorder by early next week.

Spokeswoman Sandra Groendendal said work on the recorders was still "in progress. No information can be released yet, but we will provide more information on Monday or Tuesday."

The plane had been carrying a total of 135 passengers, including 53 Dutch and 51 Turkish nationals. (dpa)