CLINTON, Ill. -- The boyfriend of a woman whose three young children drowned when their car plunged into a lake has been charged with driving under the influence on the night of the incident, authorities said Thursday.

DeWitt County Sheriff Roger Massey said police had not determined whether the plunge was an accident, or even why the car was next to Clinton Lake. He said the couple were not launching or retrieving a boat.

"We don't want to blow this up into something that it's not. But on the other side, we've got three children who are dead," Massey said.

Massey said Wednesday that the couple escaped from the car before it sank, but on Thursday he refused to elaborate and would not comment on who, if anyone, was behind the wheel when the car went into the lake.

DeWitt County State's Attorney Jerry Johnson said the boyfriend, Maurice Lagrone Jr., 28, was charged with driving under the influence and driving with a suspended license. Massey said no one was being held in custody.

The children's mother, Amanda Hamm, 28, called 911 around 7:45 p.m. Tuesday after the car went off a boat ramp, Massey said. Hamm's three children were trapped inside.

The two sheriff's deputies arrived in about five minutes, and the children were in the water for 10 to 15 minutes, Massey said. He would not give other details, including what substance or substances Lagrone was accused of taking before driving.

Christopher Hamm, 6, and Austin Brown, 3, were pronounced dead at a hospital Tuesday. Kyleigh Hamm, 23 months, was flown to a hospital in Peoria and died Wednesday.

All three children died of drowning, according to preliminary autopsy reports released Thursday.

Neighbors at the apartment complex where Hamm and Lagrone lived together in Clinton, a farming town of about 7,500, said Thursday that the couple were always outside playing with the kids.

Although Lagrone was not the father to any of the children, he treated them as his own, said Emily Strange, who lived across the sidewalk from the family. Strange said Lagrone stopped by the complex Thursday morning.

"All he did was cry. He said it's like a nightmare he can't wake up from. All he kept talking about was playing basketball with Christopher and the cool earring Austin had," Strange said.

DeWitt County Coroner Alex A. Calvert said the children had three different fathers, but he did not identify them.

Joshua E. Durbin, who lived two doors down from the family, said Hamm was constantly with her children.

"If her kids got so much as out of her sight, she freaked," Durbin said.

Lagrone was cited on July 14 for failure to wear a seat belt. That case is pending. A check of court records by the Dewitt County Circuit Court clerk found no other prior offenses.

A cross stood Thursday at the spot where the car went into the lake.

"We have a small community here dealing with some big tragedy," Massey said. Clinton is about 50 miles southeast of Peoria.

Roger Simpson, a private attorney in Monticello, was appointed special prosecutor over the case. Johnson, the state's attorney, recused himself because Hamm's mother works for his office. Simpson declined Thursday to comment on the case.