FARGO (AP) - At least one of the victims of an explosion that leveled half of a Fargo duplex and injured 13 people smelled gas before the blast, a family member says. Officials on Wednesday were looking into the possibility that a natural gas leak was the cause.

Some neighbors reported that there was lightning shortly before Tuesday's explosion, but Fargo Fire Marshal Norm Scott said Wednesday that an investigator found no evidence of a lightning strike in the area.

"It's all guesses right now," Fire Department Capt. Joe Locnikar said. He said it might be days before investigators can determine what caused the blast.

Xcel Energy turned off gas to the house and was participating in the investigation, spokeswoman Bonnie Lund said. State pipeline regulators also were part of the probe, acting as agents for the federal Office of Pipeline Safety, Public Service Commissioner Kevin Cramer said Wednesday.

Resident Mohamed Omar, 23, said his sister smelled gas prior to the explosion shortly before 12:30 a.m. Tuesday and went to the basement to check on it.

"As soon as she went downstairs, the explosion happened," he said.

The Omar family has lived in the twin home units for about three years. The family came to the United States from Somalia eight years ago and has lived in Fargo-Moorhead for about seven of those years.

Omar said his sisters also had previously smelled gas in their home.

Thirteen members of the Omar family were taken to the hospital after the explosion. Two of Mohamed Omar's sisters were airlifted to a Twin Cities hospital.

"It was like a nightmare to me," Omar said.

The explosion, which sent glass and debris flying about 50 feet in every direction, also left neighbors shaken.

The blast knocked pictures off a ledge and sent a loose piece of Sheetrock falling to the ground at the home of Brian and Jodi Hanson. Jodi Hanson's mother, Candace Quick, who also lives in the area, said the noise jolted her out of her recliner.

At least one neighbor helped with the rescue effort, which included freeing two people trapped in the leveled home's basement.