A bomb threat involving wheel-based delivery robots at an Oregon State University campus has turned out to be a prank following the reported arrest of a suspect.

Officials at the campus in Corvallis, about 70 miles southwest of Portland, sent out an urgent message on Tuesday telling students to keep away from the Starship robots, which deliver food orders to students and staff across the site.

“Do not open robots,” the social media post said. “Avoid all robots until further notice.”

Urgent OSU Alert: Bomb Threat in Starship food delivery robots. Do not open robots. Avoid all robots until further notice. Public Safety is responding.

— Oregon State University (@OregonState) October 24, 2023

The alert was in response to a threat from a person suggesting that explosives had been placed inside one of the autonomous robots, according to the Associated Press.

About an hour after the alert, the university confirmed that the robots had been taken to an isolated spot where inspections were taking place. A short while later, the incident was declared over after checks found nothing suspicious inside the machines.

A suspect was later arrested, though officials have so far declined to reveal if the person has any close connection with the campus or wider university.

However, Starship Technologies said in a statement that the bomb threat had been sent via social media by an Oregon State University student who claimed it’d been done as a joke.

“A student at Oregon State University sent a bomb threat, via social media, that involved Starship’s robots on the campus,” the statement said, adding: “While the student has subsequently stated this is a joke and a prank, Starship suspended the service. Safety is of the utmost importance to Starship and we are cooperating with law enforcement and the university during this investigation.”

Around 75 Starship robots have been delivering food to people on Oregon State University campuses for the last three years, and in May the company announced its global fleet had made around 5 million deliveries since its launch in 2014.

A number of firms have been developing similar autonomous delivery robots, including Serve Robotics, which recently expanded its tie-up with Uber Eats to deploy more than 2,000 robots at sites across the U.S. and Canada over the next year.