Royal Dutch Shell Plc referred a former vice president for sub-Saharan Africa Peter Robinson to the Dutch authorities, suspecting he may have committed crimes related to an asset sale in Nigeria.

The allegations of criminal misconduct by one of its employees come at a difficult time for Shell. Europe’s largest energy company and several former executives, including Robinson, are already facing a criminal trial in Milan over an alleged bribery scheme related to the separate purchase of a Nigerian oil block called OPL 245.

Shell denies any wrongdoing in that case. However, while investigating those charges it discovered accounts in Switzerland and a company in the Seychelles in Robinson’s name that it suspects were used to take kickbacks from the sale of another block called OML 42, said a person with direct knowledge of the matter, who asked not to be identified because the information isn’t public.

“Based on what we know now from an internal investigation, we suspect a crime may have been committed by our former employee,” Shell said in an emailed statement. “We were stunned and disappointed when we learned about this.”

Robinson worked in Nigeria for Shell from 2008 to 2011 as vice president for commercial in the sub-Saharan Africa region, part of a more than 20 year tenure with the company. His lawyer in the Milan case, Chiara Padovani, wasn’t immediately able to respond to a request for comment. She said last week that her client denies accusations of corruption from the Italian prosecutors.

Oil block OML 42, located in the Niger Delta, was sold by Shell in 2011. It produces about 100,000 barrels a day according to Neconde Energy Ltd., now the operator of the block.

The deal came into focus after prosecutors in Milan alleged that in the same year Shell and Italian oil company Eni SpA paid more than $1 billion for OPL 245, knowing that much of the money would go to pay bribes to Nigerian officials.

The criminal trial in Milan also involves Shell’s former upstream director Malcolm Brinded and the current Chief Executive Officer of Eni Claudio Descalzi. Both men deny any wrongdoing.

The criminal referral against Robinson was filed last week, said the person with direct knowledge of the matter. It appears he acted alone and took strong measures to avoid detection within Shell including encrypting emails, and failing to report companies and accounts registered in his name that fell outside the company’s protocols on eliminating conflicts of interest, the person said.

Swiss account

Prosecutors in Milan have been investigating links between Robinson and a Seychelles-based company called Energy Venture Partners. The Italian authorities suspect that part of the payment Shell made to the Nigerian government for OPL 245 was funneled through Swiss bank accounts and into Energy Venture Partners to personally enrich Robinson, said the person.

A bank account linked to Robinson was frozen by the Attorney-General in Switzerland after requests for legal assistance from the Dutch and Italian authorities, people familiar with the matter said last week. Several hundred million Swiss francs were in the account, the Tages-Anzeiger newspaper reported, citing people it didn’t name.

Shell’s own investigation concluded those accounts weren’t linked to the OPL 245 transaction, but instead may have been used for kickbacks from the sale of OML 42, the person said.

“On OPL 245, we continue to believe, from our review of the prosecutor of Milan’s file and all of the information and facts currently available to us, there is no case to convict Shell or its former employees,” Shell said by email.