From Longman Dictionary of Contemporary Englishsomebody/something is not known to be somethingsomebody/something is not known to be something or somebody/something has never been known to do somethingNOT DO something used to say there is no information that someone or something has particular qualities This species is not known to be vicious. → know
Examples from the Corpus
somebody/something is not known to be something• It is not known to be propagated vegetatively at all and can only be reproduced from seeds.• This species is not known to be vicious. 