An oil spill Thursday morning on the Plains All American Pipeline in Los Angeles near the concrete-covered Los Angeles River, which long ago was turned into a regional flood control system, was contained before it could cause serious damage.

The spill involved 10,000 gallons of crude oil that spread over a half-mile area, the Los Angeles City Fire Department (LAFD) said on its website. The fire department found a break in a 20-inch diameter crude oil pipeline early Thursday morning.

Plains All American officials were contacted and shut down the pipeline remotely, according to the LAFD report, which said runoff was quickly contained. More than 50 firefighters responded to the leak.

In a statement released to local news media, Plains All American officials said they were still investigating the cause of the above-ground pipeline leak, but initial indications are that the top part of a valve failed, allowing oil to escape in a spray.

The city’s Department of Public Health (DPH) and fire department had the situation under control late in the day, with DPH urging residents in the Atwater Village area a few miles north of downtown Los Angeles to limit their outdoor activities while strong petroleum odors lingered.

Air quality was being monitored by the South Coast Air Quality Management District, whose results showed “low risk” to the general public.

Fire department crews were able to mitigate the leak and prevent crude oil runoff into the nearby storm drain systems leading to the LA River, according to DPH. The LAFD continued to monitor the situation overnight.

The Natural Resources Defense Council (NRDC) nevertheless characterized the incident as a “geyser of crude oil shooting over Los Angeles,” asserting that it is further evidence undercutting oil industry safety claims for pipeline transportation. The spill joins recent incidents in Mayflower, AR, and the Kalamazoo River in Michigan, according to NRDC.

The environmental group attempted to tie in growing uneasiness in California regarding oil/gas drilling activity, particularly hydraulic fracturing (fracking), and the national debate regarding the Keystone XL oil pipeline from western Canada to Oklahoma into a relatively small, locally contained spill.

“Symptoms from odor exposures are not expected to lead to long-term health consequences,” the county DPH officials said.