The mother of a 9-month-old baby who drowned in a bathtub is being held on charges she left the infant unattended in the water for more than 25 minutes while discussing a drug deal, authorities said.

Katrina Lynn Brooks, 20, of Seffner, was arrested late Tuesday on an aggravated manslaughter charge. She is being held without bond in the county jail.

Brooks told detectives she left her two children unsupervised for only a few minutes to answer the door on Aug. 3 and returned to find 9-month-old Gene Vincent Kent floating in the tub, according to a Hillsborough County sheriff's news release.

The baby was pronounced dead at a local hospital. His 2-year-old sister was also in the tub, but was unhurt.

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A witness told detectives Brooks was downstairs for 25 minutes discussing a marijuana purchase before she heard the tub overflow and ran back upstairs to the children, the news release said.

Hillsborough County Public Defender Julie Holt said her office will represent Brooks but that it was too soon to comment on the case.