Rents could increase from 26 percent to 70 percent.
A studio apartment would go from $500 a month to $853 a month, and a two-bedroom apartment would increase from $725 to $915 a month.
An attorney for California Rural Assistance said the rent increases are of particular concern during these tough economic times.
The Oxnard Housing Authority says most of the 789 public housing units will not see a rent hike.
The error on 100 or so units was found during an annual review.
Rent is about 30 percent of the adjusted gross income for 85 percent of tenants, and the remainder of the families, or about 111 families or individuals, are on a "flat rate" system.
Those rents are based on a survey of rents for similar sized units in Oxnard.
The Authority does not know why the affected units had not had a rent increase since 2000.
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