Hundreds of people are feared dead across Mississippi, and New Orleans in Louisiana is badly flooded.
David Nicholson, director at the UK's Lofthouse Enterprises, which has promoted Mississippi for 12 years, said on Wednesday early-afternoon: 'There has been no official information from the state - places have been obliterated.'
Lofthouse's plans to base 2006 PR strategy around Biloxi's Ohr-O'Keefe Museum have been shelved as the building is believed to have been flattened.
It was also forced to cancel a UK media tour, planned for next week, to a seafood festival in the devastated town of Biloxi. New Orleans and Louisiana are both represented by the UK's Travel & Tourism Marketing. Its PR director Kirsty Dillury said: 'Our priority will be to get trade journalists in to New Orleans as soon as we can.'
Most of the 120,000 annual UK visitors to Louisiana visit New Orleans.
But Dillury said: 'For now, we need to flag up that (Louisiana) cities such as Lafayette and Natchitoches are open for business.'