From the Oakland Tribune, Monday, April 28, 1958. Article text:

Brussels, Belgium, April 28: A New York art film director yesterday was awarded second prize in the international experimental film competition and four other Americans won lesser awards.

The $5,000 prize went to Len Lye, New York, for his film “Free Radicals.”

The $10,000 first prize went to Walerian Borowczyk and Jan Lenica  for their Polish film “Dom” (House).

Hilary Harris, New York; Francis Thompson, New York; Stan Brakhage, Denver, Colo., and Kenneth Anger, a San Franciscan who lives in Paris won medals.

Nearly half of the 133 films entered were from the United States. There were some boos in the World’s Fair Auditorium when Belgian Interior Minister Pierre Vermeylen announced the results. An international jury studied the films for a week before deciding.

Underground Film Journal notes: This was the 2nd edition of the Brussels Experimental Film Festival.

The film for which Kenneth Anger won the medal was his second version of Inauguration of the Pleasure Dome, originally cut in 1954 and to be recut a third time in 1966.

Not determined yet which film Stan Brakhage won for. If you happen to know, please leave a comment below. Same goes for the Harris and Thompson films.