A spokesman for the Main Roads North Coast Traffic Management Branch said the screws were covering the road at Six Mile Creek in the Elimbah area and had since been cleared away.

He said there was nothing to indicate whether the screws had been dropped deliberately or accidentally, and there would be no further investigations.

Earlier

Authorities are still scratching their heads over what caused punctures to more than a dozen cars on the Bruce Highway north of Brisbane.

At least 16 cars pulled over to the side of the road between Bribie Island Road at Caboolture and Anzac Ave at North Lakes with punctures, a North Coast Traffic Management Branch spokesman said.

He said crews were still trying to find the debris.

"We think whatever got dropped must have been further north around Pumicestone Road (near Elimbah) and everyone's had a slow leak to the point where they've just pulled over," he said.

"We've been out and they've driven the whole stretch and haven't been able to locate anything so they're looking further north."

He said there were no delays because the cars were pulled over to the side of the road.

The RACQ has reported the debris was screws and bolts but that hasn't been confirmed.

Screws & bolts on the Bruce Hwy southbound after Bribie Island exit popping 16 cars' tyres! Crews on scene cleaning up #RACQ #bnetraffic — RACQ (@RACQOfficial) March 25, 2015

Meanwhile traffic delays are clearing inbound on the Pacific Motorway after a crash on the Captain Cook Bridge slowed traffic to a crawl back to Upper Mount Gravatt.

Police left the scene about 8.45am following a three-car nose-to-tail crash at 8.07am.

A police spokesman said no one was injured.