Police at the Reid Park Street Circuit during the Townsville 500. Image: InSyde Media
Officials were stood down and track action paused, impacting Aussie Racing Car, Touring Car Masters and GR Cup sessions.
Police and security onsite were believed to have been searching an area near Turns 9 and 10, which backs onto a train line.
Officials were given the all-clear to resume track action with the GR Cup just prior to 10am.
Supercars practice was scheduled to get underway at 10:35am local time but has been delayed by 20 minutes.
Qualifying has meanwhile been delayed by 10 minutes to 12:55pm, while the afternoon’s race remains at 4:15pm.
More to follow