A 15-year-old boy was in custody today on suspicion of providing an illegal drug to four fellow Mira Mesa High School students who got sick after ingesting the substance and had to be treated at a hospital.

The four freshmen began suffering from nausea while in classes at the Reagan Road campus early Tuesday afternoon, said Sgt. George Anderson of the San Diego Unified School District Police Department.

They were sent to the school nurse, who called in paramedics, Anderson said. The teens were taken to a medical center, where they were treated for their symptoms and released in the evening.

The suspect was taken into custody at the high school in the late afternoon and transported to Juvenile Hall. His name was withheld because he is a minor.

Authorities are not completely certain what kind of drug the students took, Anderson said.

"We're waiting for some tests to come back to confirm it," the sergeant said.