The two New York City siblings who have been missing since explosions killed 31 people in Brussels on Tuesday have been declared dead. Sascha and Alexander Pinczowski were in the Brussels airport on Tuesday, preparing to return to New York, when they were killed in the explosions.

"We received confirmation this morning from Belgian Authorities and the Dutch Embassy of the positive identification of the remains of Alexander and Sascha," U.S. Ambassador to Denmark James Cain said in a statement. "We are grateful to have closure on this tragic situation, and are thankful for the loving support, thoughts and prayers from all."

The Pinczowski siblings were reportedly on the phone with their mother, Marjan, when she heard a blast and the line went dead.

The Pinczowski siblings were Dutch citizens who had both been residing in NYC and planning on applying for U.S. citizenship. (Ambassador Cain's daughter Cameron was Alexander's girlfriend.) Sascha graduated from Marymount Manhattan College and resides in Manhattan, according to her LinkedIn page. She recently worked as a production intern at production and design company Shiraz Events in Chelsea. Alexander also resided in Manhattan.

Two Americans, Justin Shults and his wife Stephanie, have also been missing since the attacks; they moved to Brussels in 2014. NBC reports that the Shultses were at the airport "waving goodbye to Stephanie's mother, Carolyn Moore, who was walking toward the security check-in" when the explosions occurred.