MOSCOW — Investigators on Sunday began winching large pieces of wreckage from the Malaysia Airlines passenger jet shot down over Ukraine last summer onto trucks to transport them back to the Netherlands, the Dutch Safety Board announced in The Hague.

The Dutch investigators said that they could not predict how long the operation would last, but that it would take at least several days.

Ever since Flight 17 was shot down in July en route from Amsterdam to Kuala Lumpur, Malaysia, killing all 298 people on board, fighting in the area has interrupted attempts to study the wreckage. But the race against time has become more pressing as investigators try to finish their work before winter sets in and snow blankets the area.

The current plan is to collect as much wreckage as possible near the crash site, then take it to an airport in the eastern city of Kharkiv for a flight back to the Netherlands, the statement said. The safety board plans to reconstruct a section of the aircraft as part of its investigation.