SAN DIEGO -- A sewage spill in the College area prompted a pollution warning Monday at Dog Beach, miles to the west.

City workers discovered the wastewater overflow off 55th Street about 11 a.m., according to the county Department of Environmental Health.

By the time crews got the leak under control several hours later, roughly 50,000 gallons of effluent had entered a concrete channel that passes under Interstate 8 and eventually empties into the San Diego River in the Grantville district, the DEH reported.

A dam was installed in that location, but it was unclear how much, if any, of the contamination made it into the natural watercourse.

As a precaution, the health agency posted pollution warning signs along part of the Ocean Beach coastline, from the river outlet to the community's rock jetty to the south.

The alert will remain in effect until follow-up testing deems the area safe again for recreational uses.