The Tokyo 2020 Olympian was caught with an unlicensed AK-47 assault rifle and ammunition at his home in Iten.

Keiyo Sub County Police Commander Tom Makori said that a woman had accused the 33-year-old runner of sexual assault following a party at his home on Tuesday.

The police have also arrested an unnamed Kenyan citizen, who will face charges.

A total of 23 rounds of ammunition was found at his home when police searched the property.

"The suspect has been living in Kenya for several years," the police commander told the Standard.

"He has bought land and built his residence.

"Our preliminary investigations indicate that the AK-47 in his possession was unlicensed."

The New Zealander was banned for eight years after testing positive for EPO and submitting false documents in his defence earlier this year.

His initial four-year ban was doubled after he submitted false statements to support his claim that the EPO got into his system when he went to get a COVID-19 vaccination.

Robertson said he decided to cheat due to "frustration and anger".

"It’s been a pretty depressing and devastating day for me," he told Dom Harvey on the Runner’s Only podcast.

"There’s many reasons and it’s just not one particular reason.

"I hate it so much that it’s just a one-off hit and I got caught.

"It’s been building on me for a few years.

"Frustration and anger at the sport itself and any elite sports, I just believe it’s not a level playing field like they say."

He has a twin brother named Jake, who is also an athlete.