Unsafe value used in a resource URL in iframe

Ionic Framework ionic-v3
1

I try to display the URL in the iframe with two different way
src ="{{location.locational}}"
[src]="location.locational"
but I still get the "Unsafe value " error I don’t know what I’am missing

 <div *ngFor="let location of info">
        <h1>{{location.branchid}}</h1>
<iframe src="location.locational" width="600" height="450" frameborder="0" style="border:0"></iframe>
  </div>