A Waterloo woman has been charged with two counts of first-degree murder in connection with a deadly house fire in the city earlier this year.

Denise O'Brien, 41, was arrested by Waterloo police on Monday (Aug. 20, 2018).

Photo By: Elwin Huffman - Townsquare Media

The charges stem from an April 22 fire that heavily damaged a two-story home at 536 Dawson St. Ashley Smith, 32, and her 9-year-old son, Jaykwon Sallis, both died from injuries suffered in the fire. Three people -- a man, woman and girl -- escaped the burning house through an upstairs back window. The two females suffered minor injuries and were treated a local hospital.

Officials investigating the cause later determined an accelarant was used to start the deadly blaze.

According to Waterloo police, O'Brien has been in jail since her April 23 arrest on a variety of criminal charges. Officers took her into custody for violating of a no contact order issued on April 13 for her role in a vandalism at 536 Dawson St. Police said O'Brien admitted to being involved in an argument at the home.