Danbury Police are warning that catalytic converter thefts are on the rise across the region.  The critical component of a car's exhaust system contains expensive metals, has a street value up to $250 and takes less than a minute to remove making it attractive to thieves.  It can cost up to $4,000 to replace a catalytic converter.  Danbury Police are offering some theft prevention tips including having it welded to the car frame, installing a car alarm or having the VIN engraved on the converter.