Nearly a dozen pipe bombs, some of them already detonated, have been found on footpaths and in parks in the nation’s capital, sparking a major police investigation and warnings not to touch the potentially explosive items.

ACT police detective acting inspector Anna Wronski couldn’t say where the pipe bombs came from or who was behind them, but said the matter was being taken extremely seriously.

“We do not want members of the public to pick them up. We do not want members of the public to bring them to police stations. We want them to call triple-zero immediately,” Wronski told reporters on Thursday.

As of Thursday morning, 11 pipe bombs have been found along a one-kilometre stretch of footpath near Lake Ginninderra in Canberra’s northwest.

The first was discovered by a member of the public.

Some have been found intact over the past two days, while others appear to have gone off before being found.

“A number of the devices have been located intact, and a number have been located partially destroyed,” Wronski said.

Police don’t believe anyone was hurt when the explosives detonated.

Wronski said it was unclear how long the pipe bombs were sitting there before being discovered, and it is still unknown whether more devices will be found.

“Any explosive is dangerous. That’s why we’re taking it so seriously. An explosive in a public place does raise a lot of concern for police,” she said.

Images of the bombs distributed by ACT police show a silver piece of pipe with a cap screwed onto the top and bottom.

In one of the images, what could be a fuse extends out of one of the caps.

Wronski said the incident was not being treated as terrorism.