The servicemembers fell ill after eating at Oraifijan, a camp 35 miles south of Kuwait City.

Medical officials have tested both bottled and tap water; both came up negative. Test results on the food were expected Thursday.

The Army Veterinary Corps and the Army Medical Service Corps are investigating the incident.

Army Lt. Col. John Smith, senior veterinarian, said the Corps tracks food from commercial sites, in transit, to storage areas at “user facilities,” where preventive medicine specialists take over.

Smith said no problems were detected.

Army Col. Michael Doherty, of the Medical Service Corps, said his unit trains food handlers and inspects food service facilities and practices.

Doherty said suspect food is being tested at the Kuwaiti Armed Forces Hospital in Kuwait City. His team also was interviewing the affected servicemembers to find out what they ate.

“It could be one type of food,” Doherty said. “But we’re still checking; it’s also possible one type of food contaminated another.”

He also said that testing had ruled out anything viral.

“Definitely not,” Doherty said. “It’s bacterial. We’re doing a definitive ID process, checking for salmonella, shigella …”

“E. coli,” said Smith.

Doherty said he believed that any contamination was accidental.

The kitchen at Oraifijan is staffed primarily by “third country nationals,” meaning those who are neither American nor Kuwaiti. These workers undergo a security check by the Kuwaiti foreign ministry.

“These are contract workers,” Doherty said. “Kuwait has a lot of these people.”

U.S. contractor Brown and Root, widely reported to have been serving the food, has the contract for the kitchens there but has yet to take over the service.

Most of the 271 soldiers, sailors and Marines were treated Monday for symptoms of food poisoning at the installation and “released back to work within 24 hours,” Sgt. 1^st Class David Dismukes said.

There are around 12,000 U.S. military in Kuwait. Most are involved in exercises under a defense pact signed after the 1991 Persian Gulf War that liberated Kuwait from a seven-month Iraqi occupation.