Police have uncovered what are believed to be explosives at a property on Grenfell Street in Adelaide’s CBD.

The explosives were found about 12.30pm when officers were conducting a search at the property as part of an ongoing investigation.

Members of the Bomb Response Unit were examining the explosives and the scene on Wednesday afternoon.

Police described the items as “commercial explosives”.

Grenfell Street initially remained open to traffic, but SA Police have closed the intersection of Grenfell Street and Gawler Place.

Pedestrians have also been blocked from the intersection.

The Metropolitan Fire Service is also among emergency services at the scene.

Neighbouring cafe owner Fadi Mawlawi, whose business is about 10 metres from the building where the explosives were found, had to close his doors when the area was shut to foot traffic.

He said police arrived on Wednesday morning and he saw them detaining a man several hours before the alarm was raised about explosives.

“They must have been searching the place where he lived,” he said.

“They had him sitting on the ground floor for over an hour and then they started blocking off the area and said there was a risk of explosion here.

“It’s pretty dangerous, no one’s allowed in and out.”

Hairdresser Alexandra Salmeron, who works nearby, told the ABC she noticed a strong police presence in the area.

“It got a bit busy, a bit hectic, and then clients came in and they’re like ‘something’s going on’,” she said.

“We stayed put for the time being and waited.

“It is a bit scary – things like this happening in little old Adelaide, it’s a bit of a shock.

“There’s a lot of people in these buildings.”

Neha Pathrella said she was walking down the street when she saw the scene.

“I just hope everyone in the building is safe and has been evacuated,” she said.

“This is pretty unheard of in Adelaide, we don’t come across these situations every day.”

SA Police have told the ABC they will hold a media conference later on Wednesday to provide more information.