The bomb squad has carried out a series of contained explosions of dangerous chemicals at Gloucester Park in East Perth.

The chemicals were seized from a drug lab yesterday and taken to crime headquarters at Curtin House in Northbridge.

Early last night officers, concerned about an odour, alerted senior police who ordered the removal of the chemicals.

They were transported to the Gloucester Park pacing track early this morning inside the police armoured vehicle, the BearCat.

The chemicals were then placed in five deep holes in the middle of the park before being blown up by the bomb squad.

All track work at the park was cancelled.

The Bearcat arrives at Gloucester Park racetrack where holes have been dug to explode dangerous chemicals. ( ABC News: Graeme Powell )

Police also closed a number of roads and nearby buildings were evacuated.

The bomb squad then carried out a series of controlled explosions.

Senior Police say an investigation is underway into how the highly volatile chemicals came to be stored on the top floor of crime headquarters.

Acting Commander Scott Higgins says police did not originally believe the chemicals were dangerous.

"We're going to try and work out exactly what happened but the original indications the officers had, that it wasn't a dangerous material," he said.

"But there was something about the materials which the officers became suspicious of and then further testing showed them it wasn't what they thought it was."

Acting Commander Higgins says there will be a review of police Standard Operating Procedures, or SOPs.

"We'll be looking at all of our SOPs to see firstly if they were followed and secondly whether the SOPs are appropriate," he said.

"There will be a review of what's happened today."