Brisbane City Council was forced to close Adelaide St to all traffic at the height of the morning commute, sparking a chain reaction of traffic jams that caused chaos across the inner city.

The gridlock caused delays of up to 45 minutes on most major arterial roads into the city, with police scrambling to man intersections to improve traffic flow.

The council’s transport chair Ryan Murphy said the closure was to ensure safety.

“Unfortunately, this morning we’ve had to close a small section of Adelaide Street between North Quay and George streets which has impacted morning commuters,” Murphy said in a statement.

“This decision was made for safety reasons after a contractor reported an issue with tunnelling works beneath Adelaide Street for the Brisbane Metro project. Thankfully no one was injured.”

The south-east direction of Adelaide St was reopened at about 10.30am, but not before the emergency caused chaos for people trying to get into and out of the city.

There were reports of buses queued along the Captain Cook Bridge and Riverside Expressway, with minor crashes adding to the congestion.

Navigation app TomTom reported congestion levels 40 per cent worse than the average for Brisbane’s morning peak.