Houston  - About 1,000 inmates on Friday remained in a jail on Galveston Island, a barrier island in the Gulf of Mexico that Hurricane Ike is expected to hit first.

The prisoners and a full staff stayed in the Galveston County Jail as huge waves started rolling over the island, with Ike expected to make landfall between 0200 and 0600 GMT Saturday morning.

Mayor Lyda Ann Thomas ordered a mandatory evacuation of Galveston on Thursday.

"The prisoners and their safety and wellbeing are paramount and it will be handled," the sheriff's spokesman Ray Tuttoilmondo was quoted as saying by the Houston Chronicle.

He said the reason for not evacuating the prisoners was a security issue and could not be discussed, adding that any decision to move them would also be kept secret, according to the report.

"We did this during (Hurricane) Rita (in 2005) and no one knew until it was absolutely done," Tuttoilmondo said.

The spokesman would not comment on safety measures for the prisoners and staff if the jail were to flood. He said the structure was specially designed to withstand hurricanes.

Water levels could reach up to 7 metres in the course of the day, with waves pushing the level even higher, the National Hurricane Centre in Miami, Florida, predicted.

Fire Chief Pete David said he expected the storm to be the worst hurricane in memory for Galveston, which is known for its nearly 6- metre-high seawall built to protect historic old homes which survived the lethal storm of 1900.

In 1900, up to 8,000 people died after a huge hurricane hit Galveston, causing the deadliest natural disaster in US history. In 2005, Hurricane Katrina killed about 1,800 people in New Orleans and the surrounding Gulf coast. (dpa)