ST. LOUIS COUNTY, Mo. – St. Louis County authorities say it could be months before it is finished investigating the cause of a large house explosion on Monday.

Rodney Freeman was at work on Monday when he saw smoke filling the area. He lives about half a block away from where the explosion happened.

"It's alarming, overwhelming, frightening; wondering if it's going to happen again," he said Tuesday while assessing the damage to his home.

Five people were injured, and 20 homes were damaged on Monday. A spokesperson for the St. Louis County Police Department said it could be months before they've finished investigating the cause of this blast.

"This is not something like a one home fire that one investigator is going to look at and get to a conclusion relatively quick. This is going to take some time," Capt. James Morgan, St. Louis County Police Department, said.

As of Tuesday afternoon, an 18-year-old man is still in critical condition.

"He was conscious. He was talking to us on scene. He was able to walk out of the property on his own and we were able to get him the help that he needed as fast as we could," Morgan said.

On Tuesday, Spire restored power to yellow- and green-tagged homes. Other houses had red Xs painted on their doors. County crews swept the streets clear of debris.

County Councilwoman Shalonda Webb walked around passing out gift cards to people.

The community is pitching in, too. The Black Jack Fire Protection District had tables filled with donated items including food, clothes, and toiletries.

"It says that it's family and we're all a part of this family, so it really makes you proud of where you're at and where you serve," Fire Chief Paul Peebles said.

"As long as everybody's alive and has their health, this can be replaced," Freeman said.

Freeman expects to be out of his home for six to eight months while repairs are made to his foundation.

"I don't care if you're at the Ritz Carlton or the Taj Majal; there's no place like home," he said.

The American Red Cross has set up a shelter at Faith Church for people displaced by the blast.