Authorities say a 5-year-old boy trapped inside a burning house was killed, and his mother and teenage brother were injured.

Vallejo Fire Department spokesman Kevin Brown said in a statement that the fire is considered suspicious and the cause is under investigation.

Fire officials say heavy smoke and flames were coming from the house when crews arrived at about 10 a.m. Sunday.

Several neighbors had already tried to get inside the house to save the child, and firefighters made an "aggressive interior attack" to try to rescue him, but they could not get to him.

The boy's mother had second- and third-degree burns. The teenage boy had minor burns. The two were being treated at Kaiser Permanente Vallejo Medical Center.

The victim's names have not been released.

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