FARGO (AP) - Officials from a power company are investigating an explosion that leveled half of a duplex and injured 13 people, including two who suffered serious burns.

Investigators with the Fargo fire department could not determine the cause of the blast, which happened around 12:20 a.m. Tuesday.

"Our part of it is complete and now we're going to have Xcel Energy investigators take a look at it," said Norm Scott, Fargo fire marshal. "We are going to leave it in the hands of the experts."

Two of the victims suffered serious burns and were airlifted to a Twin Cities hospital, fire department officials said.

One child was admitted to the MeritCare Children's Hospital in Fargo, a hospital spokeswoman said. Five children were treated at MeritCare and released. Officials at Innovis Hospital were not available for comment.

Scott said the victims lived in both the north and south units of the duplex. The south duplex was destroyed, he said.

Building material, insulation, two-by-fours and pipes were strewn 50 feet in every direction after the blast, fire officials said.

Assistant Fargo Fire Chief Dean Meyer said firefighters had to use their hands to dig through the rubble to get to two of the victims who were trapped.

Eight of the residents are students at Fargo public schools, said Lowell Wolff, spokesman for the school district. Four of them attend elementary school, two at middle school and two at Fargo South High School, he said.

"Basically the (school) counselors are helping to meet the needs of the family and the friends of these kids," Wolff said.

Wolff said it's a shocking situation, "especially when 8 of the 13 are kids." He said the injured are from more than one family, but he wouldn't elaborate.