5 CANADIAN LOAN UNITS ARE SEIZED

Federal and provincial authorities have taken control of more than $2 billion (Canadian) of assets in three trust companies and two mortgage companies in a surprise move to protect depositors' interests.

Robert Elgie, minister of consumer and commercial relations in the Ontario Government, using emergency legislation passed Dec. 21, ordered the provincial registrar of loan and trust companies Friday to take control of Greymac Trust, Seaway Trust and Crown Trust.

The companies are the subject of a Government inquiry into their role in financing a series of transactions involving the sale of 11,000 apartments formerly owned by Cadillac Fairview, an international property developer.

Following the Ontario action, Paul Cosgrove, the federal minister for consumer and corporate relations, ordered the federal superintendent of insurance to seize the assets of two related companies, the Greymac Mortgage Corporation and the Seaway Mortgage Corporation. Assets Questioned

In a statement, Mr. Cosgrove said the action was taken under the Loan Companies Act, which gives the superintendent authority to take control of a company he believes has assets ''not satisfactorily accounted for and that other circumstances so warrant.''

Mr. Elgie said in a statement that he had ordered the takeover of the three trust companies because in each case, ''there exists a practice of or a state of affairs that is or may be prejudicial to the public interest or to the depositors, creditors or shareholders.''