VENTURA, Calif. (KABC) — A methane leak forced residential evacuations for several hours Thursday in a section of Ventura just blocks from an elementary school and the beach.

The exact cause and source of the leak is unclear but firefighters say the odor appears to be coming from the sewer system in the area between Bayshore Avenue and Pierpont Boulevard.

It was first reported around 11:30 a.m. Authorities issued a mandatory evacuation order for homes in the immediate vicinity and a voluntary evacuation warning for homes west of Pierpont toward the shoreline.

The evacuation order applied to all of Bayshore south of Coral Street. The voluntary warning was for residents along Pierpont between Greenock, Seaward and Harbor.

By 6 p.m. the order was lifted. Authorities say there does not appear to be any immediate danger to the neighborhood but the source remained under investigation.

Some residents told Eyewitness News they first noticed the odor several days ago after maintenance work was done to a petroleum pipeline running under their homes.