The parents of a toddler who died after he ingested illegal drugs found at their Toronto-area apartment are now facing criminal charges, Toronto police say.

Last May, the Toronto Police Service and the Child and Youth Advocacy Centre (CYAC) launched an investigation into the death of a 14-month-old boy.

Police say the boy lived in an apartment with his parents and another couple and the child died after he ingested drugs found inside the unit. Toxic levels of fentanyl, heroin and cocaine were found in his system, police say.

"After a thorough investigation which included consultation with the Ministry of the Attorney General and Toronto Police Homicide, it was determined the boy’s parents would be arrested and charged," Toronto police said in a news release on Monday.

They are each facing one count of criminal negligence causing death and failing to provide the necessaries of life.

Police have not released the names of the two accused.

Police say this investigation is the first of its kind by the CYAC, a group comprised of specialized child abuse investigators, since the unit opened in 2013.