Sascha and Alexander Pinczowksi's mother took to Facebook Thursday night to announce that the sibling's are not among survivors listed from Tuesday's terror attacks in Belgium. The State Department on confirmed Friday morning that at least two Americans were killed in the blast Tuesday morning at the departures hall of Brussels airport.
"My dearest family and friends, the Dutch Minister of Foreign Affairs released an official list of survivors from the attacks and Sander and Sascha's names were not on that list," Marjan Pinczowski-Fasbender wrote in the post.
"We thank you all for your support during these past few days, and Ed, Cam, and I have taken great strength from it. We will share any information we receive regarding final closure as soon as we can."
A close friend of the pair tells PEOPLE that Dutch officials are expected to make an official announcement regarding the apparent deaths on Friday.
"We are trying our best to get through this," Mark Lewis, Alexander's good friend, tells PEOPLE. "It feels like a dagger in the heart."
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Alexander and Sascha were preparing to fly back to New York when the first bomb went off in Zaventem airport's departures hall Tuesday morning.
They were talking on the phone to their relatives when the line suddenly went dead, friends told PEOPLE. They have not been seen or heard from since.
Officials say 31 victims were killed and 300 were wounded in terror attacks at the airport and the Maalbeek Metro Station during rush hour on Tuesday. ISIS has claimed responsibility.
After the attacks, family and friends of the siblings took to social media, enlisting the help of the public to find the pair.
"After the explosion we haven't heard from them," Lewis previously told PEOPLE. "We tried all hospitals with no luck."
He continued: "The waiting is really, really difficult. It's an absolute nightmare."
Meanwhile, Stephanie and Justin Shults, an American couple, have been missing since the airport explosions.
The two were dropping Stephanie's mother at the airport when the bomb went off.
Reporting by CAITLIN KEATING