LOS ANGELES - An American husband and wife missing since the suicide bombings in Brussels have been confirmed to have died in the attacks, according to family members and their employers.

Justin and Stephanie Shults, Belgium residents originally from Tennessee and Kentucky, were last seen dropping off her mother at the Brussels airport shortly before the check-in area was rocked by a powerful explosion on Tuesday, one of three blasts that took at least 31 lives.

"Today we learned from Stephanie Shults' family that she and her husband, Justin, were among those killed in the attack on the Brussels airport," Mars Inc, Stephanie Shults' employer, said on its Facebook page.

"We are mourning the loss of our colleague and friend. Our hearts and thoughts are with their families, and with all those who are suffering during this terrible time," the company said.

Justin Shults' brother, Levi Sutton, remembered the slain man in a post on Twitter.

"He was smart and kind and generous. I never met a single person who didn't like him. He worked hard his whole life and achieved goals that most could only dream about," Sutton said in the post.

Of Stephanie Shults, he said: "Stephanie was always so happy. I really enjoyed any chance I got to be around her. The world lost two amazing people today. It's not fair."

Justin Shults was employed by Clarcor Inc, a Tennessee-based filtration system company.

"We grieve with his family and continue to offer our support as they mourn this unimaginable loss," the company said in a statement posted on its website.

A US State Department official declined to comment out of respect for the families.

Family members of the couple had been among those waiting anxiously for word of their loved ones following the attacks at the airport and a metro station in Brussels.

At least 31 people were killed and more than 270 wounded in the blasts, which were claimed by the Islamic State militant group and sent shockwaves across Europe and the world.

On Friday two Dutch siblings who lived in New York, Alexander and Sascha Pinczowski, were confirmed to be among the dead.

The Pinczowski siblings were at a ticket counter in the airport, planning to return to New York, when the attacks occurred, news outlets reported.