Students at the University of California, San Francisco's Mission Bay campus were briefly ordered overloudspeakers to stay put because a passerby spotted what looked like an explosive device on Wednesday evening.
At about 9 p.m., police ordered people to stay where they were and cordoned off a small area at Gene Friend Way and Fourth Street while officers investigated reports of suspicious-looking pipes near a construction site, UCSF spokeswoman Karin Rush-Monroe said.
"A facilities engineer saw soil sample containers left adjacent to the construction site," Rush-Monroe said.
"He wanted to err on the side of caution, so he called it in," she said.
Luckily, responding officers were able to swiftly assess the situation and determine the pipes were not explosive, Rush-Monroe said.
"The construction company's information was on the tube," she said. "They called the company and were able to quickly verify the objects were part of the site."
No injuries were reported.