JINAN - Five people have been detained by police on suspicion of trying to cover up a gas tank explosion that killed nine people last week in East China's Shandong province, investigators said on Tuesday.

The blast occurred at 5:57 pm at Boxing Chengli Gas Supply Co, Ltd. in Boxing county, Binzhou city, according to a source with the county government.

The company initially said four people were killed in the blast, but local residents told authorities that the death toll had been under-reported.

Police investigation showed that the blast had actually left nine people dead. The five people detained are suspected of being responsible for the accident as well as trying to conceal the true death toll.

Further investigation is under way.