MEXICO CITY -- The U.S. Embassy in Mexico has narrowed its travel warning for the Caribbean city of Playa del Carmen amid what it calls an unspecified "ongoing security threat" just as the spring holiday season is kicking into high gear. The revised restrictions now say U.S. government employees must avoid five neighborhoods in and around a tourist center filled with hotels, bars and restaurants, but lift a blanket ban that had included several all-inclusive resorts.

Friday's alert also clarifies that the threat is separate from issues with ferries between Playa del Carmen and the island of Cozumel.

On Friday, CBS News correspondent Anna Werner reported that the resort, not far from other tourist hot spots like Cozumel, Cancun, and Tulum, may seem like a tropical paradise, but it has not been spared the violence sweeping other parts of the country.

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An explosion on a tourist ferry last month in Playa del Carmen left at least five U.S. citizens injured. Undetonated bombs were found on another vessel owned by the same ferry company less than two weeks later.

In January 2017, a shooting at a nightclub in the resort town left five people dead, including an American teen who was trampled while trying to escape.

Over the past year, there has been a dramatic increase in violence in and around Playa del Carmen, according to Eric Olson, an expert on security issues in Mexico at the Wilson Center's Latin American Program.

"There are American victims, but they tend to be bystanders, people at the wrong place at the wrong time," he says.

The number of foreign visitors to the resort town jumped more than 18 percent last year, and CBS News travel editor Peter Greenberg says the number of Americans killed in violent crimes in Mexico is very small.

"Every time the United States issues a travel advisory, it's got such a negative connotation, there's an almost immediate knee jerk reaction from people to cancel," says Greenberg, "but in terms of Americans being targeted for violent crime, it doesn't really exist."