Bluffton High School was on a modified lockdown Wednesday for a routine search, school district officials said.
Modified lockdowns restrict student movement within the building.
Carol McMillan, in the district's communications office, said nothing was out of ordinary about the lockdown.
Parents reported receiving an automated call or voice message sent through email about the lockdown through the district's School Messenger system.
"There is no need to be alarmed," the message stated.
Last week, a Bluffton High senior brought a loaded gun and knives to the school, prompting an hours-long lockdown at Bluffton High, and lockdowns at other Bluffton schools. No one was hurt.