A man who spent three months collecting aluminum cans to turn them into cash had his recycling business ripped off by people who saw dollar signs in the garbage bags.

Such thefts have become increasingly common recently in the Salt Lake Valley as the price of aluminum has risen, authorities say.Aluminum closed Thursday on the New York Stock Exchange at 90 cents a pound - enough to get the attention of people who need cash and see profits in unprotected aluminum.

"We have this problem with aluminum, but it happens whenever the price of metal fluctuates," said Sgt. Don Bell, Salt Lake police burglary detective.

"Copper goes high and people go up on lines and actually cut down the lines," Bell said. "It's a temporary problem that remains as long as the price is high."

Scavengers over the years have ripped off metals from Mountain Bell, O.C. Tanner, Hercules, Utah Power & Light and other companies along with cleaning out houses under construction.

Aluminum is a plentiful metal used in everything from pop cans to sail boat masts. Recycled aluminum accounts for more than a quarter of the 16 billion pounds of aluminum produced each year in the United States.

The current price of aluminum is four times higher than the price three years ago. And recycling centers have sprouted along the Wasatch Front.

"Anything that's going to bring in that kind of money is going to be an attractive problem," said West Valley Sgt. Lynn Hanson.

Hanson last fall investigated an aluminum theft at a truck stop in which thieves ripped off several rolls of wire. "But we haven't had that much of it going on that I know about in the last three or four months."

The larger companies have security guards who are aware of the attractive metal price. "For a while," Hanson said, "the difficulty of taking that in and getting money for it was almost non-existent."

People could take scrap to dealers and get cash - no questions asked. Now, dealers must get identification from those selling metals and sellers fill out forms saying it is scrap.

"People that deal in the scrap or other metals, they're in a little tighter business. It's not like a TV in a pawn shop" where a 30-day waiting period must pass before the merchandise can be sold, said Bell.

"But in scrap, you can't ask those people to do that because what may be selling at 70 cents a pound may be selling at 35 cents in 30 days," he said.

Unprotected areas have the greatest problem, and Bell said regularly watching belongings and notifying the authorities when rip-offs occur are the best things to do.

"I think you just have to be aware of it. If it's cost prohibitive for you to install alarms, you just have to be aware of it. Check on your property," said Bell.

"We had a guy that went out and spent months and months collecting aluminum cans . . . and sorted them in a shed. And in one swift night, some other person took all this bagged aluminum cans."

And reporting suspicious activity, such as people removing water heaters from homes under construction and not yet occupied, makes a difference.

"It's time consuming. It's not like running in the house and unplugging the TV set," said Bell.