Bomb squad officers have dismantled a crude explosive device in the car park of a Queensland shopping centre that police say could have caused serious injury.

A 37-year-old man and a 31-year-old woman have been charged after a large glass jar containing an explosive liquid and other unspecified "components" were found in a cardboard box inside their car.

The pair had parked a silver sedan - which had false number plates - in the car park of the Redbank Plaza shopping centre in Ipswich, west of Brisbane, on Monday morning, before the centre was open.

Channel 7

Police were called when they were seen acting suspiciously. It's understood they were caught on security cameras.

Detectives are still trying to unravel the motive after lifting an exclusion zone imposed around the car. But so far there's nothing to suggest a link to terrorism.

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Asked if the couple intended to explode the hand-made device in the car park, Senior Sergeant Gareth James told reporters: "We do not know. I do not know what gain they could have from exploding it in a car park.

"The shopping centre was not open at the time. We believe they were just parked here, the reason being we do not know."

He said the device was found in a cardboard box and was "capable of causing serious injury to people".

"All I can say is it was a fairly large glass jar which contained a substance. Not fertiliser (but) there was a liquid in it of an explosive nature. It also had a few other components which I won't go in to."

He would not say if those components included a detonator.

"It was certainly portable. But I think it's too early to speculate about what their intentions are. We don't want to cause panic out there."

The man and woman will face Ipswich Magistrates Court on Tuesday.

AAP

The man is charged with two counts of manufacture explosive without authority, and one count each of possessing dangerous goods, possessing tainted property, stealing, receiving tainted property, vehicles used on roads must be registered, drive uninsured vehicle and offences involving registration certificates.

The woman is charged with possessing dangerous goods, possessing tainted property, fraud, forgery, uttering, stealing and receiving tainted property.