St. Kitts police said Tuesday they have arrested four people in connection with an armed robbery of 16 cruise ship tourists whose bus was ambushed over the weekend.

The police announcement came shortly after two cruise ship companies temporarily suspended port calls to St. Kitts pending results of the probe into Sunday's robbery.

A police statement said scores of officers and soldiers searched several homes and cars before arresting four suspects, whom they did not identify. Authorities said they also increased patrols in areas popular with visitors.

"Investigations are continuing vigorously into this unprecedented and unfortunate incident," the statement said.

Earlier in the day, Carnival spokesman Tim Gallagher said the Miami-based company canceled a Wednesday port call by the Carnival Miracle.

He said the company is confident that "officials will have completed their investigation and done whatever is necessary to insure the continued safety of visitors" by Nov. 26, when the next Carnival ship is scheduled to arrive.

Princess Cruise Lines also called off a stop in St. Kitts planned for Wednesday, sending its ship instead to nearby Antigua

Police said masked gunmen robbed the group of tourists from the Celebrity Mercury as they were headed to the Brimstone Hill Fortress, a park popular with visitors.

Park manager Joseph Woodley told local radio the robbers blocked the road with a fallen tree. When the driver got out to clear the way, they emerged from bushes and robbed the tourists of cash and cameras before disappearing back into the woodlands.

(This version CORRECTS gender of Carnival spokesman.)