Police say an explosion struck the entrance to a kindergarten in eastern China on Thursday, with reports saying there have been casualties.

Police officials say they're investigating and have no word yet on injuries or deaths.

However, state media reports say people have been hurt and photos purportedly from the scene and posted to social media showed children and adults lying on the ground, some bleeding.

Police say the blast struck at 4:50 p.m. Thursday at the Chuangxin Kindergarten in the city of Fengxian in Jiangsu province.

It wasn't clear whether the blast was an accident or was deliberately set. The newspaper Xiandaikuaibao on its website cited an unidentified witness as saying the explosive appeared to have been a bottle of cooking gas.

Calls to the kindergarten and local hospitals rang unanswered.

Kindergartens in China have been targeted before in apparent revenge attacks carried out by people bearing grudges against their neighbors and society.

China maintains tight control over firearms and most attacks are carried out using knives, axes or homemade explosives.