San Diego.- Mexicans who have border crossing cards and are planning to vacation in the United States this summer are being reminded not to travel too far or stay too long without a U.S. permit known as an I-94.

Border crossing card holders are required to get an I-94, which cost $6, if they intend to stay longer than 30 days and/or travel 25 miles from the border. La Jolla, for example, is a tourist attraction that is about 30 miles from the border.

Border crossing cards are used by Mexicans who live near the border and travel back and forth frequently for personal or business reasons.

The number of border crossing card holders was not available but it's significant based on tourism figures for the San Diego region.

Mexican "day" visitors accounted for more than 10 percent (3.6 million) of the 30 million people who visited San Diego County last year, according to the San Diego Convention and Visitors Bureau.

An additional 310,000 Mexicans stayed overnight, according to the bureau.

About one-third of the Mexican day visitors last year came to shop. July and August were the busiest months, when 643,000 visitors from Mexico came to San Diego, according to the bureau.

U.S. and Mexican officials in San Diego issued statements recently to remind Mexican travelers not to forget to obtain an I-94 and to carry it with them at all times.

The penalties can be severe if they violate the terms of the I-94 document.

"They can be detained and their visas can be taken away," said Mexican Consul General María de los Remedios Gómez Arnau. "We've had people who've been detained overnight."

She cited cases of people returning on buses from Los Angeles who were detained because they traveled farther than they were allowed.

Mexicans who don't have border crossing cards are required to have visas to enter the country and must fill out an I-94 form upon their arrival at a land port, seaport or airport. Citizens from other countries are subject to the same rules.

U.S. Customs and Border Protection officers issue the documents. I-94 holders are required to return the "departure" portion of the document when they leave the United States.

Gómez said Mexicans from the country's interior sometimes arrive in Tijuana and use their visas to cross the border into San Diego, not knowing that they need to get an I-94.

"The airlines don't tell them because they don't know they're going to cross the border," she said.

For more information about the I-94 visit the consulate's website.

Leonel.sanchez@sandiegored.com