(Steve Ruark/AP)

Dover Air Force Base was locked down for about three and a half hours on Thursday following reports of a suspicious individual, authorities said.

The lockdown began after a suspicious individual was seen near a building on the grounds at around 11 a.m., prompting officials to close the base and tell personnel to shelter in place while they investigated. At about 2:40 p.m., the lockdown was lifted and the shelter-in-place order cleared.

“We apologize for any inconvenience and confusion this response may have caused,” Col. Randy Huiss, vice wing commander of the Air Force’s 436th Airlift Wing, said in a statement. “However, these measures were taken to ensure the safety of the base populace as we investigated the reports and found them to be false.”