(CBS/AP) LOCKPORT, La. - Emergency crews battling an apartment fire Sunday found the bodies of 29-year-old Jacqueline Gautreaux Nieves, 20-month-old Isabella Nieves or 6-year-old Gabriella Nieves inside.
Authorities say the three were stabbed, and that investigators believe the fire was set in a possible bid to cover up the crime.
"It appeared that the fire had been intentionally set, and that the three victims had been, perhaps, killed by at least one stab wound on each of the bodies," said Lafourche Sheriff Craig Webre.
CBS affiliate WWLTV reports that according to investigators, the children's father, Carlos Nieves, Jr., is now being held for questioning.
Authorities said it was Nieves who first reported the fire.
"This is a potentially complex homicide, which could ultimately result in someone being charged with a capital offense. So, our goal is to be very precise and methodical, and not rush to judgment," Webre said.
Investigators don't know if more than one attacker was involved.
He says the coroner has sent the bodies to Jefferson Parish for full autopsies Monday. Those will tell whether the three died before the fire.
According to investigators, there are no records of any domestic incidents involving Carlos and Jacqueline Nieves, who had been married seven years.
Matherne says Lockport police tell him this is the first homicide there in about 40 years.