A cargo ship slammed into a control tower in the port in Genoa, toppling it into the harbor and killing at least three people, rescue officials said Wednesday.

Four others were hospitalized and a half-dozen people remained unaccounted for, including some feared trapped inside the submerged elevator of the control tower, officials said.

Genoa police chief Massimo Maria Mazza confirmed three bodies had been extracted from the wreckage.

The crash occurred at around 11 p.m. (2100 GMT) Tuesday, during a shift change, making the accounting of personnel more difficult.

By Wednesday morning, all that was left of the control tower was the mangled exterior staircase, tilted to its side. The tower itself _ which was located on the very edge of a dock jutting out into the harbor _ was either in the water or in a heap of wreckage on the dock.

Andrea Furgani, an ambulance doctor and one of the first rescuers, said crews initially brought four injured to area hospitals in Genoa.

"The conditions were critical. They mainly suffered wounds caused by compression, broken bones and wounds on the chest," he told The Associated Press.

The ship was the Jolly Nero of the Ignazio Messina & C. SpA Italian shipping line. According to its website, the Genoa-based Messina Line has a fleet of 14 cargo ships, with the Italian-flagged Jolly Nero listed at being 239 meters (784 feet) long and 30 meters (98 feet) wide.

The ANSA news agency quoted a tearful company official Stefano Messina as saying nothing like this had ever happened before to the company, which was founded in 1921. "We are devastated," he was quoted as saying.

The Genoa port, located on Italy's Ligurian coast, is Italy's busiest in terms of overall handling of cargo, according to the port authority website.