The relatives of the 150 people who perished in the Germanwings disaster were finally preparing to put their family members to rest more than two months after the co-pilot deliberately crashed his plane into the French Alps. But bereaved families in more than a dozen countries must now wait even longer before receiving the remains of their loved ones, and some have broken their silence with “rage and despair,” the New York Times reported.

“All this tore away loved ones from families,” the families of 16 10th graders and two teachers from a German high school in Haltern am See said in a written statement Thursday. “Must more agony really be added to this pain?”

Lufthansa, the parent airline of Germanwings, emailed relatives in 17 countries Wednesday informing them the return of the remains was “temporarily interrupted” for an indeterminate period due to “new official instructions.” Airline and government officials said the delay was linked to the recent discovery of incorrect information entered into the victims’ death certificates, which rendered them invalid. It’s not yet known when the family members will receive the remains.

“When we have a fixed date, we will communicate this to the families,” Heinz Joachim Schottes, a spokesman for Germanwings, told the New York Times on Thursday, June 4. “We are working hard to be able to have this as soon as possible.

The delay has angered relatives who have so far remained largely quiet on the disaster, in which questions were raised over the circumstances surrounding the crash and whether the international airline could have done more to screen the mental health of co-pilot Andreas Lubitz. “Not only because Lufthansa allowed a depressed pilot to fly,” the families from Haltern am See explained their frustration in the statement.

“They want to have their children back,” Ulrich Wessel, the principal of Joseph-Konig-Gymnasium high school, told the New York Times. “And to bury them in their home soil.”

Investigators determined Lubitz, 27, had deliberately downed Germanwings Flight 9525 on March 24, but the exact reasons for his actions remain unclear. The co-pilot is thought to have suffered from a psychological condition and investigators described finding evidence of an “existing illness and appropriate medical treatment,” as well as torn up sick notes at his house.

Lufthansa’s chief executive, Carsten Spohr, recently proposed randomized blood tests for its pilots to check for the presence of medications that can be prescribed for certain psychological conditions. The U.S. Federal Aviation Administration (FAA) said last week a panel of experts will analyze how the FAA monitors the mental health of commercial pilots following the Germanwings accident and the missing Malaysia Airlines Flight MH370.

“All pilots are aware that you must at least take a look into all the details to find a way to reduce the likelihood of this happening again,” Markus Wahl, a spokesman for Germany’s largest pilots’ union, Vereinigung Cockpit, said in a New York Times report on Thursday.