(CNN) Authorities in Germany are investigating the birth of three children with hand deformities in a city in the west of the country.

The Sankt Marien Hospital in the city of Gelsenkirchen reported that three babies were born with "one-sided hand deformities" between June and the beginning of September this year.

"In two of the affected children, the left hand was deformed -- they had a normal forearm, but the palms and fingers were undeveloped. In another child, the right hand was affected -- here, too, the hand and fingers were undeveloped, despite a normal forearm," the hospital said in a statement

The hospital said there were no "ethnic, cultural or social similarities" between the affected families that could explain the deformities, and it noted that all lived within the local area.

"We have not seen deformities of this kind for many years. Multiple occurrences could be a random burst. However, we believe that the brief period during which we have seen these three cases is striking," the hospital said.

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