~ The state fire marshal said the exact cause of the blaze may never be known.

ANDERSON, Mo. -- Faulty electrical wiring may have sparked a fire that killed 10 people at a southwest Missouri group home for the elderly and mentally ill, and investigators were looking at whether there was any negligence by the facility's owners, authorities said Wednesday.

State fire marshal Randy Cole said the exact cause of Monday's blaze that gutted the Anderson Guest House may never be known because wiring in the north end of the single-story building, where the fire started in the attic, was destroyed.

But investigators found remains of improperly spliced wiring from the other end of the home, a converted grocery store, and Cole said the wiring was the only thing in the attic space that could have sparked the flames.

"No evidence was found that the fire was intentionally set," Missouri State Highway Patrol Sgt. Jason Clark said at news conference held by the agencies investigating the case. "Fire damage at the scene indicated that the fire had originated in the attic space of the building and had burned undetected for an undetermined amount of time before breaking through into the living space of the home."

Cole said the investigation was continuing and includes whether there was any negligence by the owners. He said the improperly spliced wiring was a violation of national building codes, but there is no state or local enforcement for those standards.

"If there is any potential possibility that we could identify an issue that could result in criminal charges, obviously we're going to pursue that," Cole said.

But he said his office had no enforcement powers because there were no state building codes. He said it might be an issue for the Missouri Department of Health and Senior Services, which regulates such facilities.

Joplin-based River of Life Ministries, which ran the home and three others like it in southwest Missouri, declined to comment on the findings or negligence investigation. A woman who answered the phone Wednesday told The Associated Press to call back later because its officers were busy.

All 10 victims died of smoke inhalation, Clark said.

Two of the bodies were recovered from bedrooms in the north end of the home, which caught fire first.

Two others were found in a hallway, investigators said. One of them was a resident and the other was one of the two overnight staff, 19-year-old Glen Taff, who was hailed as a hero by witnesses for repeatedly running into the burning building to try and rescue residents.

The other six dead were taken out as part of the rescue effort by firefighters and police, who pulled the remaining 23 residents and one caregiver from the building. Of those, 18 were still hospitalized Wednesday, Clark said.

Cole said nothing indicated natural gas from a furnace outside the north wall contributed to the fire. Maintenance work was done on the furnace Sunday afternoon.

The fire broke out about 1 a.m. Monday. It had smoldered for some time in the attic before breaking through the ceiling into the living area.

Deputy chief state fire marshal Bill Zieres said nothing was stored in the attic, but it was insulated with blown cellulose, "which can sustain a smoldering fire." Also inside the attic, Zieres said, were wooden trusses that supported the roof.

Two victims were to be buried Wednesday afternoon -- Anderson native Patricia Henson, 54, in the nearby town of Jane, and Don Schorzman, 57, in Lamar, their funeral homes said.

It was one of Missouri's deadliest fires and prompted new national calls for sprinkler systems in all assisted living centers.

The Anderson home had fire alarms but no sprinklers that could have doused the flames. In Missouri, only certain types of long-term care facilities are required to have comprehensive sprinkler systems and only in certain circumstances, such as those that house residents on a second floor.

But that law doesn't cover the single-story Anderson Guest House, which was built before 1980 -- the cutoff year under Missouri law.

After the blaze, questions persisted about the role of the group home's owner, Robert Joseph Dupont, 62, who was convicted in 2003 for his part in a scheme to bilk Medicare.

Under state law, a convicted felon in a crime involving a health care facility is not allowed to be an "operator" or "principal" in a Missouri long-term care facility.

Gov. Matt Blunt on Wednesday said he had ordered the Department of Health and Senior Services and the Department of Mental Health "to immediately assess and review all safety laws and regulations related to residential care facilities." Blunt said he asked the departments to submit a report with recommendations by the end of the year.

Dupont, who owns the land and building that burned Monday, did not respond to repeated telephone calls to his home and office seeking comment.

Dupont's wife, Laverne Dupont, reached briefly by phone Tuesday evening, told The Kansas City Star: "Everything that we're doing is legal. We're here, and we're working with the mentally ill, and we intend to keep doing that."