Reinfeldt says Billström's claim that he did not have access to insider information, and that he followed protocol is sufficient.
"I have no reason to doubt what he's saying is true," said Reinfeldt.
In a written statement yesterday, Billström insisted that he had no prior knowledge of the rescue plan.
The minister is facing criticism over his purchase of 30,000 shares in the company in February prior to news of the rescue plan being made public. The restructuring involved state-owned mining group LKAB.
According to TV 4 news, the information was available to the government five days prior to Billström making his purchase.
And according to the most recent records on government ministers' share ownership, Billström owns shares in eight companies.
Prior to his purchase in February, Billström already had 67,000 shares in Northland Resources, worth some SEK 32,000 kronor.
In the past six months, Northland's share price has lost 90 per cent in value.