Biosecurity Queensland says a second property in the state's far north has been placed under quarantine after a horse died from Hendra virus last week.

The horse died on Tuesday at Koah, west of Cairns, and tests confirmed Hendra was the cause late last week.

A spokeswoman for Biosecurity Queensland says samples have been taken from four other horses at the site and one horse at a neighbouring property.

Both properties will be under quarantine for up to a month.

Queensland Health says the four people who had a low level of exposure to the sick horse have not been tested for Hendra because they are not deemed at risk.