Forty-eight Stanford University students are recovering from a flu-like sickness, including four who were treated at a hospital for dehydration, a university spokeswoman said this morning.

The sick students, all residents of the Florence Moore Hall dormitory on campus, suffered symptoms including vomiting, university spokeswoman Lisa Lapin said.

The students started feeling sick on Wednesday, complaining of symptoms similar to the stomach flu, Lapin said.

No one yet knows what caused the students to become ill, and the university informed the Santa Clara County Public Health Department, which has launched an investigation, Lapin said.

“We reported it immediately,” Lapin said. “The cause right now is unknown.”

Four students went to a hospital emergency room to be treated for dehydration but were then released, Lapin said.

The sick students are resting and drinking fluids while the illness passes, Lapin said.

The county health department will be testing fecal samples from the students to discover what pathogen might be responsible for the illness, Lapin said.