The Martinez Refining Company in Contra Costa spewed more potentially toxic coke dust on Saturday evening, the second release in two weeks, the county said.

“Coke dust” is a byproduct of petroleum refining, and it can pose health risks to the heart and lungs if inhaled, according to the Environmental Protection Agency.

Contra Costa County said they received news of the release around 6 p.m. Saturday, and dispatched hazardous materials teams to assess the situation and potential impacts on nearby neighborhoods, as KPIX reported. The company reportedly said that the release was contained on-site and it didn't expect any off-site impacts.

But residents are still concerned about the last release, on July 11, which dropped chemicals on cars and other surfaces near the refinery. Authorities weren't notified about that release until nearly two hours later, according to the Mercury News.

A lab test of that dust found that it didn't contain high levels of toxic metals, according to KPIX. The Contra Costa Health agency’s report showed that the coke dust was chemically similar to charcoal. The local health agency and the Bay Area Air Quality Management District said they were investigating the incident to determine whether this release violated the law.

Indeed, the Martinez Refining Company has faced major blowback from an incident last year, when it released about 20-24 tons of spent catalyst starting Thanksgiving night and continuing until the next day without notifying health officials. That release contained elevated levels of aluminum, barium, chromium, nickel, vanadium, and zinc, all of which can cause respiratory problems. The FBI announced in May that it was investigating.

A toxicology report published in June said the November release didn’t pose public health risks from exposure of hazardous materials in nearby soil, but it didn’t measure the impact on those who breathed in the dust at the time. Plus, gardeners had already been warned not to eat any produce that they grew nearby.

PREVIOUSLY: Health Officials Urge Contra Costa DA To Investigate Martinez Refinery’s Unreported Hazardous Chemical Release

Feature image of Martinez Refinery via Contra Costa County.