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One girl died and another was hospitalized in grave condition after a fire tore through their Pomona apartment on Thursday morning, trapping them in their bedroom, authorities said.

The fire broke out about 10:30 a.m. at the apartment unit on the first floor of a two-story complex at 1118 E. Franklin Ave., just west of Reservoir Street, according to the Los Angeles County Fire Department.

Firefighters arrived to find “heavy fire” burning through the building, officials said.

“Unfortunately, one minor female was pronounced decease on-scene,” fire officials said in a written statement. “A second minor female was transported by paramedics in grave condition to a local hospital.”

A woman who was at the home also suffered injuries, which were described to be minor.

“It appears the two minor females became trapped in their bedroom with access to the front door blocked by fire,” according to the fire department statement. “Unfortunately, a swift escape through a bedroom window was hampered by furniture and exterior mounted window A/C unit.”

The ages of the girls were not available, nor was their relationship to the woman who was injured in the fire.

Twenty-three firefighters extinguished the flames about 25 minutes after the fire was first reported, officials said.

No information regarding the cause was available.