Los Angeles, CA (KTLA) -- The Torrance Fire Department was responding Wednesday morning after a "large explosion" was reported at the ExxonMobil Refinery.
The refinery "experienced an incident that occurred at approximately 8:50 a.m.," ExxonMobil Spokesperson Gesuina Paras told KTLA in an emailed statement.
While Paras did not elaborate on the nature of the incident, residents had reported hearing an explosion coming from the plant and feeling the ground shake, Torrance fire Capt. Steve Deuel said.
Several KTLA viewers described the shaking as feeling like an earthquake-type motion.
The blast at the refinery, which is located in the 3700 block of West 190th Street (map), was described as a "large" and "second-alarm fire explosion" by the Torrance Police Department.
The plant activated its flare system, and flames and smoke were visible in the surrounding areas, aerial video over the scene showed.
The refinery was going through its emergency procedures, according to Paras, adding that "employees are working with the appropriate agencies."
It was not immediately clear whether anyone was injured or missing. One structure, however, appeared to have been damaged, video from Sky5 showed.
Paras said the refinery was still "accounting for all personnel."
The cause of the incident was under investigation, while the amount of any damages was also being evaluated.
It was also not known where in the refinery the explosion occurred.
The incident prompted police to temporarily shut down Del Amo Boulevard between Maple Avenue and Crenshaw Boulevard.
Air quality readings were within the normal range, and an air quality warning has not been issued, officials said.
Although a warning hadn't been issued, video and photographs showed ash raining down around the surrounding on homes, vehicles, plants and roadways.
Schools in the area were initially told to shelter in place, but the order was no longer in place at every campus, according to Tammy Khan with the Torrance Unified School District. A list of schools where the warning was in place was not immediately available.
Police had also earlier stated no shelter in place orders had been issued, but a late-morning alert sent out to residents advised young children and people with certain medical conditions to stay indoors.
Those in the area were also being told not to use their air conditioning.
The refinery covers roughly 750 acres, according to Exxon Mobil Corporation. It processes an average of 155,000 barrels of crude oil per day and produces 1.8 million gallons of gasoline each year.