The death of a worker exposed to a sewage overflow at Homebush Bay's Olympic Park and who died just three days later is being investigated by SafeWork NSW.

The Herald understands the man was an employee of Veolia, which was doing sub-contract work for Sydney Water.

He is understood to have complained of light-headedness and nausea after being called to the site on Thursday, May 2. The man returned to work on both the Friday and Saturday, but died at home the following day.

It is understood several members of his work crew reported being overcome by strong fumes at the site on May 2.

In a statement on Thursday, SafeWork said: "An individual working on the clean-up later passed away."