The odor was reported at about 9 a.m., PG&E spokesman Joe Molica said.
Crews conducted a thorough search of the area around the California State University, East Bay, campus including Tennyson Road, Hesperian Boulevard and up to A Street, Molica said.
"We didn't find any evidence of any gas leak anywhere," Molica said.
Nearby schools, including Mt. Eden High School, Cesar Chavez Middle School and Schafer Park Elementary, were on alert and Tennyson High School was under voluntary evacuation, said Mig Ruiz, administrative assistant to the Hayward Unified School District superintendent.
"They just had the kids out in a field," Ruiz said.
Ruiz said the evacuation lasted for only a few minutes.
Fire department officials told Ruiz the odor may have been caused by a low tide or fumes emanating from equipment at a nearby construction site, she said.
All was quiet on the CSU East Bay campus, and the university did not carry out any evacuations, spokesman Barry Zepel said.