The object was reported at about 10:50 a.m. in the 700 block of Valencia Street, police spokesman Officer Albie Esparza said.
The Police Department's bomb squad responded to investigate the object, and firefighters are standing by in a support role, fire department spokeswoman Mindy Talmadge said.
Esparza said the 700 block of Valencia remained closed as of noon, but more information about the incident was not immediately available.
An employee at Farina Pizza& Cucina Italiana at the intersection of Valencia and 18th streets said employees at the business had not been told to take any special precautions.
ABC7 News contributed to this report.
