At least 40 bodies found in a mass grave in the central German city of Kassel could be the remains of slave laborers from a Nazi armaments factory, a city official said Wednesday.

The first four skeletons were found last week at a construction site at the University of Kassel, said police spokeswoman Sabine Knoell. Twenty-six more were found on Monday and Tuesday, and about 10 more were unearthed Wednesday, she said.

"It could well be that more skeletons will be found," she said. "We are prepared for anything."

Some of the remains appeared to have been laid out in rows, although that was not always the case, she said.