Edmonton police are warning citizens to watch for signs of cannabis extraction labs in their neighbourhoods after two recent explosions and the discovery of a third lab.

The first explosion happened in the city's southwest on April 17, while another lab exploded on May 11 in the Pollard Meadows neighbourhood in the southeast. That home, near 20th Avenue and 49th Street, was badly damaged, and is missing a wall where a front entrance would be.

On May 6, police responding to a sudden death call in a southeast neighbourhood discovered a cannabis extraction lab. The sudden death was not related to the lab, police said.

Equipment seized in the May 6 bust was displayed for the media at police headquarters on Wednesday. The display included a vacuum oven, compression pumps, double boilers, refrigeration coils, butane cans and a sample of shatter.

Police say all three labs were producing shatter, a resin-like cannabis concentrate that contains high levels of THC. It's typically smoked in small amount by using a vaporizer pen.

The dangers of the labs are mostly due to the use of solvents like butane or propane. The vapour from a regular-sized can of butane has the capacity to destroy a 1,450 square foot home, police say.

A sampling of shatter was on display at police headquarters on Wednesday. (Travis McEwan/CBC)

The butane and cannabis are used in pressurized and heated system, which extracts the THC from the blended cannabis flower. A vacuum converts the liquid butane to vapour, making it easier to remove it from the system with the use of a pump.

Although using cannabis is legal, the production being done in these extraction labs is illegal.

"Depending on what we find if they're producing using solvent, we can charge them with production under the Cannabis Act," said Sgt. Guy Pilon of the EPS Clan Lab Response Team. "You're not allowed to produce it using solvents."

Police also displayed equipment used in a cannabis extraction lab. (Travis McEwan/CBC)

Pilon had anticipated a rise in concentrated cannabis production, as the products cannot be found in legal cannabis stores.

"There's money to be made from those who produce it," Pilon said. "And so I was anticipating that we would find a few of these. Certainly this is probably the biggest commercial amount of equipment that I've located in one residence that wasn't exploded."

Watch for telltale signs

Police are warning for residents to watch for signs of cannabis extraction labs that may be using solvents. One of the easiest things to watch for may be multiple butane canisters inside or outside of a home, police say.

"A 16-ounce can, if completely opened and fumed out property into a house, would create an environment that would blast the house," Pilon said.

@Travismcewancbc

Travis.mcewan@cbc.ca