Radar Online: Police were called to the Gosselin house in Wernersville, PA Thursday night after Jon and Kate got into a heated argument over Stephanie Santoro, the nanny who was on duty that day

As RadarOnline.com previously reported, on at least one occasion, Jon has spent the night with Santoro, 23, a former cocktail waitress, single mom and aspiring model whose online resume reveals she's willing to pose nude!

One source close to the situation told RadarOnline.com, "Kate showed up at the house unexpectedly. It's Jon's scheduled time to be there with the kids."

Jon was inside the home and wouldn't let Kate in.

Kate reportedly started screaming at Jon at the fence outside their once happy home about his relationship with Santoro - the nanny hired by Jon, and not Kate.

Amid all the screaming, someone called 911. Police arrived, but no arrests were made. Kate left and checked into a local hotel.

As the couple's marriage has unraveled, so has the civility between them. "Kate couldn't get access to the house. She was upset," said the source.

And although Jon may have spent the night with Santoro in the past, he is still romancing 22-year-old Hailey Glassman.

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