The thirty additional researchers, who were sent to Kharkiv last week to investigate MH17 crash, returned to the Netherlands due to unstable security situation in eastern Ukraine, Dutch Prime Minister Mark Rutte said Friday."At the moment it is simply not safe enough to send our people in the field and that is also the judgment of our international partners Malaysia and Australia," Xinhua quoted Rutte as saying."A group of 20 people stays in Kharkiv, which will ensure that we remain on operational strength," he added.On Sep 12 the prime minister announced the arrival of the additional investigators due to hopeful developments since the ceasefire in Ukraine. The aim was to get back to the crash site again, but they did not reach that goal.Rutte emphasised that the group of extra soldiers and police sent last week have done their work. "All preparations have been made for the return of the mission as soon as possible," he noted.On Aug 6 the Dutch government decided to stop the recovery and repatriation mission on the MH17 crash site until further notice due to the deteriorating security conditions in the area.The plane crashed July 17, killing all 298 people on board.