St. Louis Park Fire Marshal Cary Smith was visiting an office complex a few weeks ago when he spotted something most people would miss: brass valves on parking ramp standpipes that firefighters use to feed water to their hoses were missing.

Earlier, at a community ­center, he'd noticed a brass swivel ­missing from a water pipe that juts from the outside wall.

Once he would have attributed the missing parts to vandalism. Not anymore.

"I think it's economically motivated," Smith said. "It's scrappers who are … taking as much brass as they can."

Since late last year, police in Bloomington, Edina, Eden Prairie, St. Louis Park and other cities have reported a rash of brass thefts from parking ramps and buildings with sprinkler systems. The valves and swivels apparently are being stolen by thieves who are trying to capitalize on prices for scrap brass that have reached $2 per pound.

Cities have increased police patrols in ramp areas, advised building and ramp owners to regularly check for missing pipe connections and asked the public to alert police to suspicious activity. The thefts are not only expensive — 10 valves taken from an Eden Prairie mall parking ramp were valued at $4,000 — but missing connections create a safety threat, especially when taken from apartment buildings, schools and office buildings.

"This can be a life-and-death issue at buildings," Smith said. "If those caps or plugs are missing, pipes can be plugged with rocks or birds' nests and ... we might not be able to connect with the [water] system at all."

In March, two men were arrested in St. Louis Park after suspicious activity at a church, where they were caught with part of a standpipe. They have not yet been charged. But police in several cities said they consider their investigations still open.

Because most fire rigs are too big to fit into parking ramps, fire departments need a source of water there. Standpipes have brass connections that ­firefighters can hook a hose to when water is turned on.

If those connections are missing, water simply pours out of the pipe or the standpipe lacks the pressure to charge the system, said Vic Poyer, Bloomington police commander.

"They are removing the whole assembly, or cutting the pipe," Poyer said. "We have nothing to hook up to. This is definitely a public safety issue."

In Edina, seven ramps have been hit since the first of the year, many of them in the Southdale area. Some ramps had a couple of dozen fixtures taken at a time, said Tom ­McKenzie, an Edina police detective. In one location, thieves also cut off about 300 feet of copper piping.

"I've been doing this for 27 years and I've never seen brass standpipes taken," McKenzie said.

Bloomington had about 15 thefts, mostly in parking ramps in the Interstate-494 strip and office areas, and in the northwest corner of the city. Eden Prairie fire officials discovered missing brass in three parking ramps.

"Ramps are easiest because there is easy access and ­minimal security," said Tom Schmitz, an assistant fire chief in Eden Prairie.

Smith said the St. Louis Park parking ramp lost six valves last month, the second time it had been hit by brass thieves. He said brass fixtures have been taken from two schools, a school maintenance shop and community centers.

Scrap yards have been notified about the spate of brass thefts through crime alerts. In the past, most have been cooperative and notified authorities if someone brought in unusual amounts of one item.

Despite the thefts, brass ­fittings are preferred for water connections because they are strong and don't corrode. Some cities, including St. Louis Park, are trying to stop theft of brass swivels from buildings by installing locking caps that prevent swivels from being removed.

"It seems to be working," Smith said.

He has encouraged ramp owners in his city to make examination of standpipes part of their security routine.

"They should make this part of their regular walk-through," he said.