Brittany Murphy and Simon Monjack's deaths could have been partly caused by mould found in their house.

The actress and her husband died within six months of each other, with both deaths attributed to pneumonia.

Now, the investigation into their deaths is being handled by the Department of Public Health, with mould now being considered a relevant factor to the respiratory health of the pair, according to gossip website TMZ.

The issue of mould in their West Hollywood Hills home had been noted when investigations were made into Brittany's death in December 2009, but at the time it wasn't considered to be a "contributing factor".

Investigators have been allowed to enter the home to check the effects of the fungi by Brittany's mother Sharon Murphy, while Simon's mother is flying to the US from Europe to keep informed on the studies.

Recently Simon's spokesperson Roger Neal confirmed the British-born screenwriter needed heart bypass surgery, but had postponed it because he was too busy.

He said: "Simon needed a bypass. I was told he needed a bypass and I said to him, 'Simon, you have so much going on, let's keep you healthy.'

"I said, 'You want to be healthy don't you?' He said, 'Yes,' but he said, 'The bypass can wait.'

"I don't know how much of an emergency it was. The doctors would have made him get it immediately if he needed it. But Sharon Murphy confirmed with me he did need a bypass.

"They didn't make it public because he had so much going on."