Major hotel, casino and online travel agency stocks were hammered anew on Wednesday, as a flurry of earnings warnings prompted by a sharp drop-off in U.S. travel wiped millions more dollars from a sector that has lost nearly $13 billion in market value this week. 

Since trading resumed on Monday, most major hotel stocks have lost 30 percent or more of their value. Casino stocks fared slightly better, while online travel agencies took the biggest drubbing, losing nearly 50 percent of their value. 

The continuing slide came amid a growing series of earnings warnings from the sector for the third and fourth quarters. 

Most companies said it was still too early to quantify how the air attacks in New York and Washington on Sept. 11 would affect their business, but all said they expect to post numbers below forecasts. 

Hotel companies that said they would miss their previous guidance included Hilton Hotels Corp., Host Marriott Corp. and France's Accor SA, operator of the Motel 6 and Red Roof Inn chains in the United States. 

Among gaming companies, Mandalay Resort Group warned that some layoffs would be necessary to offset reduced business levels, according to a published report. And among online travel agents, Sabre warned that its third-quarter earnings would be lower than expected. 

``We think for the next six to 12 weeks that we will see extraordinary times in our business, probably the worst we've ever seen in terms of business travel,'' Hilton Chief Executive Stephen Bollenbach said in a Wednesday morning conference call, echoing the sentiments of many. 

Among the major hotel stocks, Starwood Hotels & Resorts Worldwide Inc. took the biggest drubbing, with shares down 36 percent midway through the Wednesday trading day compared with their close before the attacks. 

Hilton shares were down 34 percent over the same period, while shares for Marriott International Inc., which manages most hotels owned by Host Marriott, were down 29 percent. 

Collectively, Starwood, Hilton and Marriott International have lost $6.4 billion in market capitalization since trading resumed on Monday. 

Among major gaming companies, shares were down the most for Mandalay Resort, with the company's stock down 31 percent since trading resumed. MGM Mirage shares were down 29 percent, while Park Place Entertainment Corp. stock was down 27 percent and Harrah's Entertainment Inc. was down 19 percent. 

Collectively, the industry has lost $3.3 billion in market value since trading resumed. 

Among online travel agencies, meanwhile, shares for the industry's two biggest players -- Sabre Holdings Corp. and Expedia Inc. -- were both down about 45 percent. The two companies have lost a combined $3.1 billion in market value since trading resumed.