CALLAHAN, Fla. -

The father of a 9-month-old baby who drowned in a bathtub last month pleaded not guilty at his arraignment Thursday.

Robert Jerrell, 33, is still being held without bail on a charge of aggravated manslaughter of a child.

Investigators said Jerrell had taken a 2-year-old from the tub but left his baby, Aaron, alone in the bath at their home on Marlee Road in Callahan while he helped find a gasoline can for a relative.

When he returned, the baby was unconscious in the water.

The baby's grandmother said it was an honest mistake.

"It's a misunderstanding between the two brothers because one brother thought the other had got the other out," she said.

The Florida Department of Children and Families is also investigating the death.