Port Hueneme in Ventura County, California was closed off Monday afternoon while authorities investigated a possible terrorist threat on a cargo ship, a port official said.

The action came just before noon after a dockworker discovered a possible threat written in the cargo hold of a ship carrying bananas from Guatemala, said Will Berg, the port's marketing director.

Port Hueneme, 60 miles (97 km) north of Los Angeles, California, is seen in this undated aerial handout photo. Authorities closed a major California port on June 26, 2006 after finding a written threat, apparently directed at U.S. President George W. Bush, in the hold of a cargo ship. [Reuters]

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 was written in English and 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, officials said.

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 aboard the 30,000-ton refrigerated vessel which arrived from the Port of Quetzal in Guatemala were evacuated, Berg said. Workers already outside the port were being kept out, though anyone inside was allowed to remain.

The 135-acre 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, the nation'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.