KIRKSVILLE, Mo. (AP) – Investigators said Monday they were looking at the possibility that seven people found dead in an apartment were killed by carbon monoxide.

The victims – including a woman and her two young children – were discovered Sunday after a 911 caller reported a “strange odor.”

Police Chief Jim Hughes said a fire department carbon monoxide detector gave a high reading, but he said police were consulting with the maker of the detector to determine exactly what that reading meant, and they had not located the source of the poisonous gas.

The home heating system was functioning properly, but a van parked in the garage was taken to a crime lab for analysis, he said.

Hughes would not speculate on the possibility of foul play. He said he expected autopsy results by Tuesday.

Police did not immediately identify the victims. But Lisa Lewis, who was among about 30 people who gathered later Monday to remember the victims, said her daughter, Maranda McDermott, 23, and McDermott’s children, Adam McDermott Jr. and Melina McDermott, were among the dead. Adam turned 1 on Thursday, and Melina would have turned 2 on Dec. 30.

Relatives identified two of the other victims as Jeremy Liner, 19, and Reginald Washington, 21. The other victims were a 21-year-old man and 21-year-old woman.

Lewis said the children had a 4-year-old sister who wasn’t home at the time who she was now caring for. She said the girl’s father died last year.

The victims were found in three rooms. Hughes said it did not appear any tried to get out of the house. He said authorities weren’t sure how long the victims had been dead.

The duplex is a few blocks from the Truman State University campus in Kirksville, a town of 17,000 residents about 30 miles south of the Iowa state line.