LONDON (AP) — Information about possible links between a Russian businessman who died in mysterious circumstances and U.K. intelligence services will remain secret for security reasons, a British judge said Tuesday.

Judge Nicholas Hilliard is leading an inquest into the death of Alexander Perepilichnyy, who collapsed and died while jogging near his home south of London in November 2012. Police initially said the 44-year-old died of natural causes, but the inquest is considering whether he might have been murdered.

Before his death Perepilichnyy had been helping Kremlin critic Bill Browder expose a $230 million Russian tax-fraud operation.

Lawyers for Perepilichnyy's insurer, Legal and General, asked to see any evidence about possible links between the Russian and U.K. intelligence agencies.

Legal and General attorney Bob Moxon Browne said the nerve-agent poisoning of former Russian spy Sergei Skripal and his daughter in March showed "the lengths to which the Russian state are prepared to go to make an example or punish people perceived as enemies, traitors or turncoats."

The British government argued against releasing material connected to the intelligence services.

Hilliard said in a written ruling that the material in question was "marginal" to resolving the question of how Perepilichnyy died.

"I am satisfied that the balance comes down in favor of non-disclosure," he said.

The long-running inquest is due to resume Friday.

After the poisoning of Skripal and his daughter in the English city of Salisbury, the U.K. government said it was looking again at the deaths of 14 other people linked to Russia. It said this month it did not plan to reopen any of the investigations.

Skripal and his daughter were released after long hospital stays. Authorities have not disclosed where they are living now for security reasons.