NORTH PHOENIX - Strong chemical odors wafting through a neighborhood may be a sign of working methamphetamine laboratory.

There are less obvious indicators, such as Dumpsters filled with unusually large quantities of matches or empty cold-medicine boxes.

Members of the Cactus Park Community Alliance, a coalition of neighborhood groups in northwest Phoenix, were urged last week to watch out for these guideposts.

Meth labs "are absolutely everywhere" but especially common in north Phoenix, said Darin Fredrickson, a veteran drug investigator for the Phoenix Police Department.

Fredrickson talked to nearly three dozen alliance members during a gathering last week at the Deer Valley Community Center, 2001 W. Wahalla Lane.

Cmdr. Joe Klima, head of the Phoenix police drug enforcement bureau, said meth is a big factor in property crimes and violence throughout the city.

"Many problems can be traced to people trying to fuel a meth addiction," Klima said.

Businesswoman Robin Mofford, a Cactus Park alliance leader, said Fredrickson was invited to address the group because "knowledge is power."

The more that is known about methamphetamine, the more alliance members will be able to spot trouble when a lab shows up in their neighborhoods, Mofford said.

Fredrickson, an 11-year of the Phoenix force, offered a mock demonstration on how to manufacture the drug, saying the ingredients and lab equipment can be purchased at supermarkets, hardware stores and animal-supply outlets.

Fredrickson said that ephedra, an herb found in cold medicines and dozens of other over-the-counter products, is a necessary ingredient.

Illegal drug manufacturers will stock up on large quantities of such products then extract the ephedra in cooking up batches of meth, he said.

That's why large quantities of empty drug-medicine boxes are a dead giveaway for a working meth lab, he said.

Fredrickson said meth cookers also need red phosphorous, an ingredient that can be extracted from the strikers on matchbooks and match boxes.