Authorities in Iowa are investigating a case of nursing home residents being photographed in the nude.

Over the weekend, officials identified three of four nursing home residents who were photographed naked.

The elderly residents at Greenwood Manor in Iowa City don't know who took the photos, or why they were taken, said Sgt. Troy Kelsay.

"They were not sexually explicit photos," said Kelsay. "They were more embarrassing photos. They looked as if they had been posed."

Authorities began investigating last month after a North Liberty woman reported receiving the photos appearing to show residents of Greenwood Manor. She identified one of the people as her sister. No other family members received copies of the photos, as far as police can tell, Kelsay said.

Police are investigating several suspects with possible access or motive. He said any criminal charges will depend on the photographers intent, which wasn't immediately clear.

Greenwood Manor owner Jerry Nicholls said he sent a letter to the about 50 residents' families notifying them about the photographs.

He said the center had made security changes since they became aware of the photos, including banning cell phones from the building.