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.

According to preliminary examinations by the coroners' office, the corpses are somewhere between 50 and 100 years old. Knoell would not speculate, however, on whether they could have died during wartime bombing or were possible victims of Nazi crimes.

"But we are, naturally, in contact with historians," she said.

The area where the skeletons were found was the site of a factory that built locomotives and tanks during World War II, where Nazis forced thousands of slave laborers to work, said Kassel archivist Frank-Roland Klaube.

The evidence speaks against them being regular factory workers buried quickly after an Allied bombing attack, he said.

"Among other things, there were no rings or watches found on the corpses," he said.

It is also known that in other areas of Kassel the SS, Adolf Hitler's dreaded paramilitary organization, shot and hastily buried other victims in the final days of the war, Klaube said. Still, there have been no reports of mass murders on the site of the new discovery, he added.

The area was the site of a military hospital until 1870, and it could be that the bodies were people who died there, he said. But that would mean that the bodies are older than is currently believed.

Experts are testing the remains to try to determine how and when they died, Knoell said.

"We are very curious to see what the experts find," she said. Results are not expected until next week at the earliest.