Students and employees at Sidwell Friends returned to the school’s Wisconsin Ave. NW campus after a brief evacuation Thursday morning, according to school officials.

President Obama’s two daughters are enrolled at the private school.

According to a message posted on the school’s web site, the school was evacuated after it received a “suspicious phone call.”

It did not detail the substance of the call.

“After an investigation by law enforcement,” the web site read, “it was determined that no risk was present.” By 12:30 p.m., most public safety workers had left the school and students were back in class or at play on outdoor fields.

Assistant Head of School Ellis Turner said students were evacuated from buildings but remained on Sidwell grounds for about an hour while authorities investigated.

A fire department spokesman confirmed that members of the department were at the school Thursday morning. He referred further questions to the police department, which did not immediately return calls.

Secret Service spokesman Brian Leary declined to answer questions on the matter Thursday.

Turner said he could not recall another incident in which Sidwell was evacuated because of a suspicious call.

Rachel Karas contributed to this item.

This item has been updated.