Brazilian researchers on Thursday said they found signs of the Zika virus in a common mosquito that is a separate species from the insect known to be the primary means of transmission.

They warned, however, that further tests are needed to determine whether the species, known as Culex quinquefasciatus, is in fact responsible for transmitting the virus to humans and, if so, to what extent.

The scientists, from a leading Brazilian research institute known as the Oswaldo Cruz Foundation, discovered the Zika traces in Culex mosquitoes captured in and around the northeastern Brazilian city of Recife, capital of the state that was hit hardest by the Zika outbreak since last year.