Two children suffered burn-type injuries to their mouths and throats after drinking what they believed to be apple juice at a Chinese buffet in Pennsylvania, and authorities said today they are investigating the cause.

The children remained hospitalized in fair condition, three days after their visit to the Star Buffet and Grill outside Lancaster, about 70 miles west of Philadelphia.

A 10-year-old boy and 4-year-old girl suffered blistering and were vomiting, said Lt. Robin Weaver with the East Lampeter Township Police. He said a third child, who had stomach discomfort, and an adult who tasted the liquid but did not swallow it, also required hospital treatment.

“There apparently was some unknown caustic substance in the apple juice,” Weaver said.

Star Buffet manager Steve Weng said he did not know how it happened and regrets that it occurred. He said the juice was poured into disposable cups from a half-gallon bought at a local grocery store.

The restaurant remained open during the weekend.

The state Agriculture Department sent an inspector to the site today after learning of the incident from news accounts. Spokeswoman Shannon Powers said the inspector was reviewing how cleaning chemicals are stored and labeled, among other things.

Weaver said the county prosecutor’s office and the U.S. Food and Drug Administration also are investigating. Authorities were obtaining translators to interview restaurant employees who spoke only Spanish or Chinese.

The apple juice was recovered and was being tested.

The 10-year-old boy’s father, Richard Zaragoza Sr., told LNP news in Lancaster they were at the restaurant to celebrate a birthday when the children became sick.

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