DENVER (AP) -- The Food and Drug Administration is working with the Centers for Disease Control and Prevention to determine the source of contaminated cantaloupe blamed for a multistate outbreak of listeriosis.

Several Colorado grocery stores have removed cantaloupe from shelves, though there has been no official recall.

More than two dozen people infected with the outbreak strain of Listeria monocytogenes have been reported in Colorado, Indiana, Nebraska, New Mexico, Oklahoma, Montana and Texas, and four have died. Health officials say most consumed whole cantaloupes, most likely marketed from Rocky Ford in Colorado.

Jensen Farms in Holly, Colo., is voluntarily recalling cantaloupe it shipped to Illinois, Wyoming, Tennessee, Utah, Texas, Colorado, Minnesota, Kansas, New Mexico, North Carolina, Missouri, Nebraska, Oklahoma, Arizona, New Jersey, New York and Pennsylvania between July 29 and Sept. 10.

(© Copyright 2011 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)