Fans were clamoring this week for details surrounding the arrival of JAY-Z and Beyoncé’s twins after it was revealed that the Gemini babies arrived a week ago. However, a Tuesday report said the twins — a boy and a girl — remained in the hospital for treatment after they were born prematurely.

TMZ reported previously that the twins remained in the hospital as the result of a “minor issue.” The gossip site’s Tuesday report said that Beyoncé may not have had a full-term pregnancy, and her babies have reportedly remained at the hospital “under the lights.” 

“Our sources say the babies are ‘under the lights’” TMZ reported. “They would not be more specific, but that often means the babies have jaundice because of elevated bilirubin levels. The lights are designed to lower bilirubin in the blood to eliminate the jaundice.”

Read: What Are Beyoncé’s Twins’ Names? Twitter Makes Suggestions While Stars Remain Quiet

According to the American Pregnancy Association, premature babies are sometimes put under bili lights, or the bright blue fluorescent lights in a baby incubator, which help treat newborn jaundice.

As TMZ noted, the bili lights are used to lower the bilirubin in blood that causes newborn jaundice, or the yellowing a baby's skin and the whites of their eyes. As Romper reported Tuesday, the condition is fairly common and occurs roughly 60 percent of the time in premature births.

In its initial report from over the weekend, TMZ reported that the Carter babies were being held in in the hospital after a “minor issue” surfaced. Unnamed sources told the site that doctors did not feel comfortable releasing the children from care. At the time, details around the cause of the issue were not known.

“One source told us Beyonce also remains at the hospital, but as far as we know she's okay,” TMZ reported Sunday. “The babies are expected to be okay as well.”

Read: Beyoncé Twins Born? Singer Is 'Hiding' Babies, Fans Say

People reported Saturday that the couple are “thrilled” by the arrival of their two children, who will join their older sister 5-year-old Blue Ivy as the most recent additions to the Carter family. According to an unnamed source close to People, “Bey and Jay are thrilled and have started sharing the news with their family and closest friends.”

Beyoncé made the announcement on Instagram in February with an image from the first of what would later become numerous maternity shoots shared on the platform with her 103 million followers. To date, the post has garnered well over 11 million “likes.”

“We would like to share our love and happiness,” she wrote in February. “We have been blessed two times over. We are incredibly grateful that our family will be growing by two, and we thank you for your well wishes.”