The first death was that of 35-year-old Shyla Stylez.
It is not clear if any of the five models who have died recently knew one another.
So far, no reason has been given for her death.
In December, actress August Ames, 23, hanged herself in California, where she lived with her husband.
Hay said it was merely a 'coincidence' that the two most recent deaths were of women who belonged to his agency.
It is not known how she got the substances into the facility where she was being treated for addiction.