An anonymous donor paid for hotel rooms for several dozen homeless people who had been camped out in tents in Chicago as temperatures dipped to dangerously cold levels Wednesday. The good Samaritan picked up the hotel bill for about 70 people after donated propane tanks that kept them warm in subzero temperatures were confiscated, the Chicago Tribune first reported.

The homeless had set up tents in a makeshift camp near an expressway in Chicago, where temperatures plummeted to 22 degrees below zero. They were using propane tanks that were donated to them –– until one exploded Wednesday afternoon, prompting a response from the Salvation Army, a spokesperson for the organization, Jacqueline Rachev, told CBS News.

The blast didn't injure anyone but it caused a small fire, which led the Chicago Fire Department to take away the propane tanks, leaving the homeless encampment without a source of heat.

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The fire department warned of the dangers of propane tanks on Twitter: "During extreme cold weather, we understand that people want to help our homeless population However, we ask that under no circumstance should you donate propane tanks which are potential fire hazards. Propane tanks can cause potential fires and explosions."

According to Rachev, she was notified to set up for the group at the Salvation Army's warming center, but then she got word about the anonymous donor's act of kindness.

"All the folks there, some wonderful citizen is going to put all of them up at a hotel for the rest of the week," she told the Tribune. She didn't know the exact location of the hotel, but said it was somewhere on Chicago's South Side.

The donor's generosity made sure dozens of people in need had a warm place to sleep when conditions outside were life-threatening. At least nine deaths are now connected to the polar vortex that's spreading dangerously cold air and causing major disruptions across the Midwest and Northeast. Nearly 90 million people are in the path of the extreme cold weather system.