A fire that erupted at a Las Vegas apartment building early Saturday morning killed at least six people and injured 13, officials said.

Authorities said they are investigating the fire that broke out at the Alpine Motel Apartments, a three-story complex in downtown Las Vegas. Initial reports showed that it appears to have been accidental, a fire official told reporters.

The fire department earlier said five of the injured were in critical condition and that several residents were hanging out of windows as firefighters arrived. Several jumped and were injured, the department said.

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Tim Szymanski, the public information officer for the fire department, told Fox 5 Las Vegas that the fire originated on the first floor of the building before spreading. He said when crews arrived, multiple people were seen hanging from windows on the second floor.

Heavy smoke and high heat were coming from the building, the station reported.

The incident reportedly happened at around 4:15 a.m. Later that morning, the Red Cross announced that it was helping people at a nearby school.

According to Las Vegas Fire & Rescue, at least 50 people were displaced by the fire. The damage is currently estimated at $475,000, KTVN reported.

No firefighters were injured.

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The station reported the fire may be the second deadliest fire since the 1980 blaze at the MGM Grand Hotel where more than 80 people were killed.

The Associated Press contributed to this report.