American couple Justin Shults and Stephanie Shults missing after Brussels attacks

An American couple is among those missing after fatal attacks occured in Brussels Tuesday moing.

Justin Shults, 30, and Stephanie Shults, 29, had just dropped Stephanie's mother, Carolyn Moore, off at Brussels Airport when two bombs detenated, killing multiple people. 

\"Her mom is fine but no one has been able to contact Justin or Stephanie,\" Justin's brother, Levi Sutton, told NBC News.

\"She doesn't know if Justin and Stephanie watched her as she headed towards security or if they tued to leave the terminal,\" Moore's sister, Betty Newsom, told WLEX. \"We don't know for sure if (they) had been able to get out of the airport or if they were still in the airport.\" 

Sutton said the Shults have not been listed on any casualty reports and both their cell phones have been going straight to voicemail. 

The couple, both accountants, moved to Brussels in 2014.

\"All they can really do is go from hospital to hospital looking at the list of people that have been identified as injured,\" Newsom said. She said Moore is \"of course very frightened and very worried about her daughter.\" 

\"The situation is still fluid, but we are working with local authorities to locate and assist any U.S. citizens affected by the attacks,\" said State Department Spokeswoman Pooja Jhunjhunwala. Right now, she says there are \"no updates.\"

At least eight Americans were injured in the attacks, including three Mormon missionaries.