GLEN ELLYN, Ill. (CBS) — A recreational vehicle owner has a warning for others — park at Wal-Mart at your own risk.

As WBBM Newsradio’s Regine Schlesinger reports, it’s one of the unwritten rules of the road – RV owners know they can generally park overnight in Wal-Mart lots. The Daily Herald reports Wal-Mart is even known as “America’s Campground” by RV owners looking for a place to spend the night for free.

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LISTEN: WBBM Newsradio’s Regine Schlesinger reports

Larry Socha of New Jersey has camped out overnight in Wal-Mart parking lots often, with his $1.2 million motor home. But the Daily Herald reports recently when he drove into the Chicago area to attend his 50th high school reunion, his RV was towed away from the parking lot of a Wal-Mart in Glen Ellyn while he was running errands for his 90-year-old mother.

Socha had thought the RV had been stolen, but soon discovered that Wal-Mart had it towed off the lot, the Daily Herald reported.

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A Wal-Mart statement says the retail giant considers RV travelers among its “best customers,” the Daily Herald reports. But RV owners are advised to contact management before camping overnight in a store lot, the newspaper reported.

Wal-Mart spokeswoman Kayla Whaling tells the Daily Herald the manager knocked on the door of Socha’s RV a couple of times before it was towed.

Socha told the Daily Herald that he had parked in the same Wal-Mart lot for three or four days with no problem last year, and this time, he didn’t even see the signs warning that “truck parking” is not allowed and violators can be towed. Socha also told the newspaper he saw the Glen Ellyn Wal-Mart parking lot listed in an online directory of free overnight parking lots, although Whaling told the paper that Wal-Mart does not keep any such list.

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Socha had to pay $872.50 to get his RV and its contents back, the newspaper reported.