When you check into a hotel, could you be sleeping on dirty sheets?

An Inside Edition investigation found that some hotels did not change bed sheets between guests.

At a Residence Inn by Marriott in New York City, Inside Edition used a harmless washable fluorescent paint to spray "I slept here" on the bottom sheet of the bed.

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The paint is not visible to the naked eye. It can only be seen when a UV light is shined on the sheets.

We checked out — leaving the bed looking as though it had been slept in — and booked the same room for the following night under a different name. When the sheets were pulled back and a UV light was shined on the bed, the words "I slept here" were still there.

"This is absolutely disgusting," said Inside Edition's Ann Mercogliano.

A manager was called to the room. At first, she didn't want to talk about the findings.

"Why weren't those sheets changed?" Mercogliano asked her.

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"We make it a custom to change every checked out room sheet," she responded. "However I do not know what happened in this situation."

The Marriott Corporation apologized and said it takes these issues very seriously. They are now inspecting the room to ensure this does not occur again, they said.

Inside Edition checked in to nine different hotel to check their sheets. Tune in on Tuesday to see what was found under the covers at other hotels.

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