HARBIN -- Five workers in Northeast China's Heilongjiang province were killed while repairing sewerage equipment ahead of heavy rain, said local rescuers on Wednesday.

Liu Yanfei, from Harbin, capital of Heilongjiang, was called out to repair a dysfunctional pump at about 9:30 pm Tuesday. He inhaled toxic fumes while working, causing him to faint and fall into the water.

Several of his colleagues attempted to save him, only to fall into the water as well.

Two of the workers were later rescued, while five others, including Liu, died.

Rescuers suspect that the fumes were methane. A thorough investigation has been launched to identify the gas.

Many northern cities in China experienced heavy rain Wednesday, resulting in waterlogging.