Four people including a toddler were killed Tuesday and two more people were taken to hospitals after an early morning trailer home fire in southeast Ohio, state and county officials said.

Neighbors calling 911 reported hearing an explosion just after 4 a.m. Fairfield County Sheriff Dave Phelan said those reports were under investigation, and the cause of the fire was unknown.

"Oh my God! ... The trailer across the road just blew up," reported the first caller, whose name wasn't included in an audio recording released by the sheriff's office. " I'm going to say they're probably all there. Oh my Lord! Something just blew up over there. Holy crap!"

Phelan said authorities were searching for a possible seventh person who might have been inside the trailer home, which collapsed. No identities or information about the relationships of those inside were immediately available.

"It's completely gutted," Phelan said. "There are partial walls that are up, but the inside is completely gone."

He said a woman who appeared to be badly injured was taken to Ohio State University's medical center, some 40 miles northwest of the rural lot where the trailer stood, outside the village of Sugar Grove. A man was transported to nearby Fairfield Medical Center. The sheriff didn't have information on their conditions.

Phelan said firefighters from seven departments responded, hindered on hilly two-lane roads by overnight snowfall. Fairfield County was under a Level 1 snow emergency, meaning motorists were urged to be very cautious because of hazardous conditions.

The Ohio State Fire Marshal's office sent investigators to the site, which Phelan said was still smoldering several hours later.

The trailer fire was the third multiple-death home fire in Ohio in less than four weeks.

Three children were killed in a Dec. 12 house fire in Hamilton, in southwest Ohio, and a woman and three grandchildren were killed Dec. 26 in a fire near Washington Court House, about 40 miles southwest of Columbus.

Fire Marshal's spokeswoman Lindsey Burnworth said Tuesday that investigations of those fires were continuing.

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Associated Press writer Kantele Franko contributed in Columbus.

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Contact Dan Sewell at http://www.twitter.com/dansewell