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Two 13-year-old boys have been arrested in connection to a fire that engulfed a California city's public library and left one firefighter dead and another missing, authorities said Wednesday.

The fire broke out at around 4 p.m. Tuesday at the library in Porterville, a city of around 60,000 in California's Central Valley, about 70 miles southeast of Fresno, the Tulare County Sheriff's Office said.

Porterville fire Capt. Raymond Figueroa, 35, was killed in the blaze, and firefighter Patrick Jones, 25, was still missing on Wednesday morning, authorities said.

Figueroa has been with the department since 2007 and Jones since 2017, officials said. The fire was finally brought under control in the middle of the night.

“Unfortunately they are still in the process of searching" for the missing firefighter, Tulare County fire Capt. Joanne Bear told NBC News. "Obviously with the damage to the building, there's a still an issue of safety getting in there."

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The pair of 13-year-old boys from Porterville who have been arrested have been booked on suspicion of arson, manslaughter and conspiracy, authorities said. They were not identified due to their age.

"Immediately after the fire started, members of the Porterville Police Department and Porterville Fire Marshal received information that two young men had ran away from the library," according to a joint statement by the city's police and fire departments.

"Detectives with our Department began an investigation, even prior to the fire personnel determining whether this fire was accidental or not."

Library worker Tameran Anzivino said she was in the building when the blaze began and ushered others inside out to safety.

Anzivino called the fire "heart-wrenching.”

“This is the beloved Porterville city library. It’s the hub of the city and it's heartbreaking to see it go down like this,” she told KSEE.

The blaze quickly grew in the library, which is just yards away from the city's fire station, NBC Fresno affiliate KSEE reported.

"Please join Sheriff Boudreaux, and all of us at the Tulare County Sheriff’s Office, in sending our deepest thoughts and prayers to the Porterville Fire Department," the office of Sheriff Mike Boudreax said in a statement on Facebook.

A witness to the blaze, Clara Rojas, told the TV station, "It's impacting on everyone, I think."

Porterville has a median household income of $41,246, with 29.8 percent of the population living in poverty, according to the U.S. Census.

The City Council last month discussed the possibility of either renovating the library or building a new one, which officials said would cost upwards of $33 million, according to The Porterville Recorder.