ST. PETERSBURG, Fla. (AP) - Carnival is investing about $400 million to clean up the air pollution from the massive diesel engines it uses to power more than 70 cruise ships.

The company said Thursday it was spending more money and putting the technology in more ships than initially planned.

Emissions from oceangoing vessels had largely been unregulated, but in 2010, officials created buffer zones along U.S. coasts and required foreign-flagged ships to reduce pollution.

The technology Carnival will use is similar to what power plants and cars have done to reduce pollution. Carnival will deploy scrubbers to reduce sulfur dioxide and use filters to trap soot on the ships.

At port, the ships will plug into the electrical grid, rather than idle, or use a lower sulfur fuel.

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