The massive fire destroyed the 1.2-million-square-foot warehouse and paper products inside, causing an estimated $500 million in damage.
Linda Nguyen has been placed under arrest for the deaths of her two daughters, according to the Ontario Police Department.
Police say a mother acted alone in the murder of her daughters, ages 4 months and 14 years old. The teen was a special needs child, police said, and the mother was "dealing with some depression" prior to the incident.
Two earthquakes - a 4.4 magnitude and 3.4 magnitude - struck a little more than 2 miles north of La Verne, according to the U.S. Geological Survey.
Ontario police arrested a 34-year-old mother for allegedly leaving her young children in a hot car with no air-conditioning for at least 30 minutes while she shopped at Walmart.
A fight in the Ontario Mills Mall food court where someone involved used a Taser caused a scare Saturday night.
