An estimated 300,000 gallons of sewage spilled into Gunpowder Falls in northern Baltimore County due to a vandalized manhole, county officials said this afternoon.

In a wooded area southwest of Cub Hill Road, a manhole cover was found removed yesterday afternoon by a local resident.

The 12-inch sewer line was blocked with rocks, causing raw sewage to dicharge into a tributary of Gunpowder Falls.

Baltimore County crews brought in heavy equipment and used an emergency “pump-around” to direct sewage around the blocked line. The overflow was stopped at 10:00 a.m. today, according to a news release.

The Baltimore County Health department is monitoring water quality in the area and will publish a water-contact advisory if necessary on its website.