An explosion that ripped through a Minneapolis apartment building on Wednesday morning is still under investigation, and residents say there may be people who are unaccounted for.

The blast injured 14 people, some of whom suffered from burns and some who broke bones when they attempted to jump to safety. Authorities say that at least six of those injuries are critical, and a local news source says that there are three people unaccounted for.

“We’re not certain whether people jumped out of windows, or fell out, or were pushed out by the explosion,” said Robert Ball, the information officer for the local EMS. “The intensity of the fire means they have not been able to conduct a complete internal search.”

The fire was heavily involved by the time emergency crews arrived, especially on the second and third floors. Witnesses say they saw several people jumping from windows to safety, as a matter of seconds might have meant life or death.

“Crews made entry into the first floor of this structure, but conditions became very untenable very quickly,” Chief John Fruetel said.

Frutel said that nine of the ten apartments in the building were occupied, but it wasn’t immediately clear how many people were living in each one. Because the roof collapsed, a thorough search has been made nearly impossible; adding to the difficulty of the investigation is the weather, as temperatures plummeted and the water used to fight the fire froze on the building and sidewalk below. The conditions were hazardous for the firefighters, said Ball.

”While heat-related illnesses are common for firefighters, now you combine that with the rapid onset of frostbite or hypothermia when they come out and they’re wet and exposed to bitter cold temperatures,” he said.

The cause of the explosion is still under investigation.

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