(Corrects gender of official in 3rd paragraph)
* 14 companies across 9 countries under investigation
* Fund excludes companies on ethical grounds
* Watchdog says Petrobras needs to do more to reform
By Joachim Dagenborg
OSLO, Jan 28 (Reuters) - The ethics watchdog for Norway's $800 billion sovereign wealth fund, the world's largest, is stepping up its scrutiny of companies the fund invests in to make sure they are not involved in corruption, an official at the watchdog told Reuters.
Eli Ane Lund, administrative leader of the ethics council, said the watchdog was currently investigating 14 companies for suspected corruption across nine countries.
These include Brazilian oil firm Petrobras, which is currently mired in the country's biggest ever corruption scandal, she said, while declining to name the other companies.
"There is a clear increase in the number of corruption cases the council on ethics is looking at," Lund said in an interview.
"Before we based ourselves a lot on media reports. Now we look at companies across a sector and go thoroughly through it."
Norway's sovereign fund has a range of criteria to ensure the country's oil wealth is invested ethically, excluding companies involved in severe environmental damage, nuclear weapons making, tobacco production and labour exploitation.
The ethics council gets its mandate from Norway's parliament and makes recommendations to the board of the country's central bank, which supervises management of the fund. The board then decides whether to follow the council's advice.
The fund, one of the world's largest investors, has so far excluded 65 companies and has two under observation, including Petrobras.
Earlier on Thursday, it warned the state-owned Brazilian firm it needed to more to reform to avoid the fund withdrawing its investments.
"We have had a dialogue with the people at Petrobras who are implementing the new systems, and we don't have confidence that this will be done in a satisfactory manner," Irmela van der Bijl Mysen, a senior adviser at the ethics council, told Reuters.
The discovery of price-fixing, bribery and political kick-backs at Petrobras led it to write off $17 billion of over-valued assets in 2015. Its shares hit a 13-year low this month.
"The management has to take a clear responsibility and admit their share of mistakes," Van der Bijl Mysen said. "That would have been a signal by them that they take this seriously. They have to be much clearer about their share of responsibility."
At the end of 2014, the Norwegian fund owned a $163 million stake in Petrobras International Finance, a subsidiary incorporated in Luxembourg, and a $38 million stake in Petrobras Global Finance, incorporated in the Netherlands, according to the fund's annual report.
Petrobras was not available for comment.
Additional reporting by Stine Jacobsen in Oslo and Silvio Cascione in Brasilia; Editing by David Goodman and Mark Potter