The The National Center for Missing And Exploited Children website has now posted pictures of Alyssa and Alex Allen.
Their father's photo is also included.
The kids were last seen with Alvin Allen by clerks at Roses in Cary's South Hills Mall
Their mother, Susan Boggs, says she dropped her twins off last Sunday to visit with him, but they have never returned.
"Getting out the word as much as possible. If anybody's seen them, please call report that you've seen them because you know were going on a week now that they've been without their medication too. That's what's starting to worry me a little bit," said Boggs.
Boggs says both of her twins have breathing conditions that require medicine their father doesn't have.
She believes Allen took her children to avoid having to pay child support. They were due in court for a hearing on the matter this month.
If you have any information, you're asked to contact Erwin police or call the National Center for Missing and Exploited Children at 1-800-843-5678 (1-800-THE-LOST)