The RCMP have launched an investigation to determine what motivated teenagers in Langley, B.C., to manufacture explosive devices that were found in park on Friday, prompting the evacuation of several blocks.

RCMP bomb squad members were called Friday to deal with 11 explosive devices that were dumped in a Langley park.
(CBC)

An RCMP bomb squad was called to detonate 11 explosive devices, which had been dumped in a duck pond in Sendall Gardens, located in Langley's 50th Ave. and 201-A Street area.

A 12th device was found inside the residence of one of two 17-year-old girls who were taken into police custody Friday.

"These [were] actual explosive devices,'' said RCMP Cpl. Peter Thiessen, adding that each was the size of a cigar holder.

He said all of the individuals who were involved in manufacturing the devices were known to each other in a variety of different ways, including through their attendance at a local school.

But what motivated the teens to manufacture "highly volatile'' explosive devices isn't yet clear.

Thiessen said police believe there is a link between the explosives dumped in Sendall Gardens and the homemade bombs that injured two youths in Langley City on Monday.

On the same day, a friend of the injured youths was severely burned when a bomb he was carrying exploded outside a retail store in Langley.

On Thursday, another explosive device was found in a planter outside the Metrotown shopping mall in Burnaby, B.C.

The person who found it walked with it through the mall and handed it over to security.

After the mall was evacuated, police removed the bomb with a robot and safely blew it up.

Thiessen said the activities of the Langley bomb manufacturers put an entire community at risk, and resulted in an expensive police investigation.

"If charges are warranted, we will be forwarding charges,'' he said.

With files from the Canadian Press