Seven people have died after falling into a septic tank in Poland while trying to rescue a colleague, rescue services said.

All were overcome by toxic gas as they tried to save their co-worker from the pit in Karczowka, in western Poland, a fire service spokesman said on Thursday

"One person fell into the septic tank while emptying it and the others were trying to rescue this person and also fell in",

Magdalena Bilinska, a spokeswoman for the local fire service, told local news on Thursday.

"We can confirm seven deaths and one person in very grave condition," she said, adding that the survivor was a woman.