Updated

A Southern California port was closed off for several hours Monday afternoon while authorities investigated a possible terrorist threat on a cargo ship, authorities said.

The closure at the Port of Hueneme in Ventura County came just before noon after a dockworker discovered a threat written in the cargo hold of a ship carrying bananas from Guatemala, said Will Berg, the port's marketing director.

There was some discrepancy in the exact phrasing of the message.

Berg said it read: "This nitro is for you Mr. George W. Bush and your Jewish cronies."

Federal authorities said it read: "Nitro + glycerin my gift for G. W. Bush and his Jewish gang."

The message, scrawled in marker on a metal pillar within the ship, was being investigated by federal authorities, including the FBI and Secret Service, as well as local officials.

FBI spokeswoman Laura Eimiller said agents were at the scene. No nitroglycerine or other explosives were found during a thorough search by bomb personnel, she said.

Divers were called in to inspect surrounding waters.

About 20 people were evacuated from the 30,000-ton refrigerated vessel, identified as the Wild Lotus, which arrived from the Port of Quetzal in Guatemala on Sunday evening, officials said. Workers already outside the port were kept out during the closure, though anyone inside was allowed to remain.

The port was reopened around 3:30 p.m., and workers resumed unloading two other ships while the investigation continued, police Cmdr. Jerry Beck said.

The 135-acre (55-hectare) port, located northwest of Los Angeles, consists of two terminals. It is the only deep-ocean port between Los Angeles and San Francisco, though it handles far less cargo than the Los Angeles-Long Beach complex, America's largest harbor.

It is the top seaport in the United States for citrus exports and ranks in the top 10 in the country for imports of automobiles and bananas, according to the port's Web site.