Authorities have given the all-clear at Bladensburg High School after they found a "suspicious backpack" during a sweep of the school.
The sweep was conducted after someone called a bomb threat in to the school.
The backpack had what appeared to be wires sticking out of it. A bomb squad deployed a robot to inspect the backpack.
Authorities said they were operating out of an abundance of caution. They will continue to investigate who phoned in the threat.
Students were evacuated from the school shortly before it would have let out for the day.
Classes will resume Thursday.