Two Pennsylvania children are listed as critical but stable after they each drank an unknown caustic substance in their apple juice at an all-you-can-eat buffet on Friday. Richie Zaragoza, 10, and his 4-year-old half-sister Ginaya Mendoza, are being treated at Hershey Medical Center for severe burns of the mouth and throat, LancasterOnline.com reported.

The scene unfolded at Star Buffet & Grill where the family had been celebrating Richie’s birthday. Shortly after Ginaya drank the juice and began vomiting, Richie started throwing up blood and yelling that his throat was burning, Virginia Davis, his mother, told LancasterOnline.com.

The pair were rushed to Hershey Medical Center where they spent Saturday night in the intensive care unit. Richie’s father, Richard Zaragoza Sr., told the news outlet that his son has cystic fibrosis and diabetes, and has been sedated with an intubation device. Doctors are still investigating blood in his urine, LancasterOnline.com reported.

“I had to try to talk to him last night through his fingers,” Zaragoza told the news outlet. “I told him I loved him … and he squeezed my hand twice so he was responsive.”

According to reports from the family, Ginaya is no longer sedated.

Preliminary tests have revealed that methanol was identified as at least one of the substances present in the tainted juice, but the investigation is still ongoing. The restaurants manager told LancasterOnline.com that the juice came from a local supermarket.