Australian Federal Police (AFP) are investigating the source of a threat against police officers in Brisbane today.

Authorities received a tip-off via the National Security Hotline.

This prompted the partial lockdown of the AFP building on Wharf Street in the inner-city suburb of Spring Hill and the Queensland Police Service headquarters on Roma Street in the CBD.

The Queensland Police headquarters still has a partial lockdown in place and will until the Commissioner declares there is no longer a threat.

The AFP building has reverted to its usual tight security that does not allow public access.

Sniffer dogs trained to detect explosives swept the AFP building during the lockdown.

The Queensland Police lockdown at the Roma Street headquarters was ordered just before midday, a spokesperson said, without being able to give a reason.

Staff at the Queensland Police building can come and go, but only through one door.

Last month, the terror threat level against police across Australia was raised to 'high', in line with the threat against the general population, meaning an attack against a police officer was likely, but not imminent.