Police at Pudong New Area's Shanggang residential community are desperate for clues as they are challenged by possibly the strangest case they have ever encountered.

A woman surnamed Ding, reported to the police on Saturday that her apartment in the Shanggang No.1 community had been broken into. The intruder doesn't seem to have entered to steal things, but to leave mysterious "paintings" on the walls.

According to Ding, the invader stole nothing but a bottle of Dettol disinfectant.

What terrified Ding is that the invader drew graffiti on her walls with a pencil "borrowed" from her daughter.

The "paintings" covered almost all of the walls in her apartment and looked like wall cracks, Ding told Xinmin Evening News.

"The paintings looked so real that at first I believed my apartment suffered a severe earthquake," Ding said.

"When I touched the 'cracks,' I found they were erasable," she continued.

She said the invader probably finished the painting in two hours, while she and her daughter were out shopping.

She also found it strange that despite the intruder having to get through three doors to gain entry, none of them appeared to have been forced.

A police officer surnamed Li said they were still investigating the case. "I've never heard of anything like this in my career as a policeman," said Li.

"It's strange that the intruder broke into a building just to do artist creations."

He believed the incident, which was apparently a prank, was probably conducted by a person with mental problems, as he said there were many mental patients living in the complex.

Moreover, Li said they had not ruled out the possibility that it was Ding herself that "committed the crime" to attract attention to herself.