DENVER -- The Web site for Foothills Park & Recreation was hacked and personal information, including credit card numbers, may have been stolen, officials said Wednesday.

Foothills Executive Director Ronald Hopp said they started having trouble with the Web site last week. Originally the problem seemed to be a virus, but, he said, they now believe it was a cover for someone to hack the site and steal personal information.

Technical staff discovered Monday morning that the files were compromised and possibly stolen, Hopp said.

The district has hired a security consultant to figure out how the site was hacked and how many people's information was compromised.

Hopp said the number of people affected would be "very significant."

"It is very disturbing that despite the security measures that were in effect, a rogue hacker was still successful in obtaining this information," Hopp said. "Additional protections are being installed, and on-line registration will not be available until these measures are implemented."

The Jefferson County Sheriff's Office is investigating the hacking, said spokeswoman Kate P. Dragoo.

People who registered for classes either online at ifoothills.org or at one of the Foothills Park & Recreaction facilities should take action to protect their identity from thieves, Dragoo said.

She said users of the site or the facilities should request a fraud alert be placed on their file with the three major credit monitoring agencies (Equifax, Experian and TransUnion).

You can also request a credit report from each agency and review them carefully.

The district has created an information page on its Web site. The Web site contains helpful phone numbers, information on next steps to take, and links to credit reporting agencies. In addition, the district has set up a special number at 303-409-2124 to answer specific questions not addressed on the Web site.

The district operates several recreation centers, outdoor swimming pools, the Foothills Golf Course and the Meadows Golf Course. The district serves about 90,000 residents.