Two 13-year-old middle school girls were held on assault charges Wednesday after being accused of serving poisoned cake to about a dozen students who became ill and went to a hospital.

Lawyers for the two seventh graders said the cake was a prank, and that they had no intention to harm anyone. Lab tests showed the icing on the cornbread cake contained an expired prescription drug, bleach, clay and tabasco sauce.

"They took it into the cafeteria at lunch time and began passing it out to students, just whoever would take a piece," said Jay Dillon, spokesman for the Cobb County School District (search) in suburban Atlanta.

Some of the students started vomiting after eating the cake Tuesday, officials said. Eleven students, mostly seventh graders, were treated at a hospital and released, Dillon said.

"There was some hysteria, from what I understand," Detective Wayne Delk said.

The 13-year-old girls appeared Wednesday before a Juvenile Court judge who refused their attorneys' request to allow them to go home. The judge will reconsider the request on Friday.

Police said one of the teens was charged with 12 counts of aggravated assault with intent to commit murder, among other charges. The other girl was charged with the same 12 aggravated assault charges.

In addition to the charges, Dillon said the girls will be suspended and could be expelled.

"We don't understand why they would have done something like this," Dillon said. "It's certainly something more serious than a prank."