HOUSTON -- Three small children are in the hospital after they were trapped in a house fire early Thursday morning.

Family members believe the fire started in the kitchen. 

"We want the fire department to come back and re-investigate this," said Robert, a family member.

Firefighters responded to the home around 12:15 a.m. They saw flames and smoke coming from the right side of the house. They knocked out the fire and searched the area twice.

"While conducting the secondary search, we did discover the three fire victims," said Assistant Chief Omera Longoria of the Houston Fire Department.

The children, 10-year-old Patrick, 8-year-old Angel and 5- year-old Jerome, were home alone when the fire broke out.

Investigators said they were treated on the scene and then rushed to local hospitals.

The fire department said the children’s mom had left the kids with the grandparents for the night.

"They were babysitting five of their grandchildren. They did leave for a short time, and left the three kids at the residence. When they returned, the fire department was on the scene," said Longoria.

A family member said the grandfather is devastated.

"He's feeling terrible. His daughter left the children with him --in his very responsible hands," said Robert.

The grandfather reportedly tried to run into the house and save the children. 

"The fire department stopped him. They grabbed him, but he went in anyway on his hands and knees,” said Robert. “But they got to him before he could get to the children.”

The oldest two children are now in a San Antonio burn hospital. While the youngest child could go home as soon as tomorrow.

The mother of the children is apparently in San Antonio with her other two children.

The entire family said they are praying for the kids recovery.