City officials are struck by the frequency of the missing hardware - city workers have replaced 46 storm and sewer covers in the past month at a cost of $78 apiece, said Bob Ellinger, Columbus' sewer maintenance manager.

Usually, only one or two manhole covers are stolen each year, usually in the Ohio State University area and when big parties are held.

Police, who have also noted the disappearance of aluminum bleachers and benches, are contacting local scrap yards to remind them that only authorized city workers are allowed to dispose of metal products, according to a memo from Lt. Michael Broberg.

Authorities said a thief could profit from a recent jump in the prices of scrap metal.

Three years ago, scrap steel sold for $75 a ton. Last week, the price was $203 a ton for composite steel, said Chuck Carr, spokesman for the Institute of Scrap Recycling Industries Inc.

City officials are worried that missing manhole covers, giving way to 10-foot drops, could lead to injuries.

"If the manhole (cover) is missing, it would look just like a dark spot. You could very easily fall in there," Ellinger said.

The owner of one Columbus scrap yard said he didn't think manhole covers would be a likely target for thieves.

Manhole covers, which weigh about 90 pounds each, would fetch the seller about $2, said Mark Masser, owner of Masser Metals.