Oregon State University warned students Tuesday that its campus’ food delivery robots could be carrying explosives after a prankster activated a false bomb threat.

“Do not open robots. Avoid all robots until further notice. Public Safety is responding,” the university said in an alert just before 12:30 p.m. local time.

Security quickly rounded up the campus’ 20 Starship robots in an isolated location on its Corvallis campus, located 80 miles southwest of Portland.

“Robots are being investigated by technician,” OSU said in a follow-up alert.

The school lifted the emergency order after an hour when a student came clean and admitted the whole thing was a hoax.

San Francisco-based Starship Technologies, which makes the robots, said OSU sent a bomb threat over social media that involved the campus robots.

“While the student has subsequently stated this is a joke and a prank, Starship suspended the service,” the company said in a statement, adding that it would resume later in the day.

Representatives for the school said they would continue investigating the validity of the bomb threat in spite of the student’s admission.

“The OSU Department of Public Safety is following protocols for this evolving situation to protect the safety and security of OSU’s students, staff and visitors, which is our top priority,” Rob Odom, vice president of university relations and marketing, said in an email.

The fleet of unmanned androids uses GPS technology to wheel around the 500-acre Corvallis campus to deliver food to students and staff who order through the Starship app

The school introduced the six-wheeled white bots in 2020, making it the first campus in the state to have autonomous delivery robots.