SAN DIEGO (CBS 8/CNS) - Extra police officers will be posted at an Allied Gardens school Thursday after a threat prompted a campus lockdown.

A tip that someone may have made some sort of threat against Lewis Middle School prompted the roughly 90-minute campus lockdown Wednesday while authorities investigated the situation.

San Diego police got word of the possible threat shortly before 1 p.m., SDPD spokesman Humberto Hernandez said.

Administrators secured students in their classrooms while officers performed a methodical search of the campus, with bomb-sniffing dogs, in the 5100 block of Greenbrier Avenue.

Officials lifted the lockdown shortly before 2:30 p.m., said Ursula Kroemer, a spokeswoman for San Diego Unified School District. There were no reports of anything hazardous found at the campus.

The FBI initially received the tip about the potential threat, the nature of which was unclear, Hernandez added.

A man in his twenties was detained and questioned, but he has not been named a suspect.