The mother of two children found dead Monday morning is in custody and is suspected in their death, Wilmington police Chief Robert Tracy said.

Tracy said the boys, who he estimated to be about a few months old and 5 years old, were dead when police arrived shortly after 8:30 a.m. Monday for a welfare check. The boys' mother was one of the people who called police, Tracy said.

The boys could have drowned, Tracy said, although there was a strong smell of gas when police arrived at the home in the 800 block of W. Ninth Street. Because of the smell of gas, officers evacuated the building and opened doors and windows.

“Yes. It’s definitely the person that has the authority over the house at this time is always considered the suspect,” Tracy said. “But, you know, we have to rule everything out before we make that determination.

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“We are interviewing all parties and witnesses at this time.”

Several officers stood outside the house on the corner of West Ninth and North Adams streets Monday morning into the early afternoon. Investigators could be seen through a first-floor window, near where a baby chair stood. Later, investigators and state prosecutors walked in and out of a back entrance of the three-story brick building that houses at least two apartments.

The state's forensic investigators arrived on scene about 11:25 a.m.

Neighbor Aunjea Daniels, 25, said she often saw the woman and her children outside their home.

"She seemed like a happy parent," she said. "She was usually uplifting. She seemed happy and her children were well-groomed. I would have never thought she would do something like this, but you just never know what's going on behind closed doors."

A woman who stood across from the house watching the activity said she could smell gas when she went to see why the fire trucks were there.

“It was very strong,” said the woman who would not provide her name. “I thought it was a gas leak.”

The woman said a Delmarva worker who’d entered the house to deal with the leak, told her it was something different.

“He told me about the tragedy,” she said.

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Dorothy Hartman, a 60-year-old neighbor, said she was shaken by early reports of what had occurred. The incident comes just weeks after a young man was shot outside her bedroom window, she said.

"I've got to get out of Wilmington," she said as she held up her trembling hands. "I know stuff like this happens everywhere, but not in your front yard."

Bernadette Sturgis, who lives a block away, said she never saw the family living at the home.

"I'm flipping," the 50-year-old said. "I just feel so sad for those kids. Who would do something like that?"

As television reporters were preparing to give their live feeds around dusk, Outreach Minister Margaret Guy, who runs the Stop the Violence Prayer Chain, held a prayer vigil outside the structure.

“We are out here today to pray for the families,” Guy said. “We are out here today to pray for healing for our city. It’s too much."

With about two dozen children and adults, the groups prayed for the two children who died. There have been about 30 homicides in Wilmington so far this year.

This is a developing story. Check back with delawareonline.com for more information.

Contact Esteban Parra at (302) 324-2299, eparra@delawareonline.com or Twitter @eparra3.