CHICAGO (CBS.MW) - Investors unloaded 14 percent of Costco's share value in heavy early trading Tuesday after the wholesale club warned that quarterly profits could dive as much as 18 percent.

Costco shares plunged $5.01 to $31.95.

Hobbled by higher healthcare costs and worker's compensation coupled with lower margins, the Issaquah, Wash.-based retailer slashed its fourth fiscal-quarter earnings outlook to a range of 46 cents to 48 cents a share, down from a previously expected 54 cents to 56 cents a share.

Costco noted in March that high worker's compensation costs - particularly in California - was at the heart of weaker-than-expected results. The company has said that while only one-third of its workforce is in the West Coast state, those employees absorb more than two-thirds of annual workers' compensation costs even though injury rates are in line.