Since May 2017, special counsel Robert Mueller has been probing Russian interference in the 2016 election.

The Mueller investigation has been a lucrative source of profit for some online gamblers who bet on the likelihood of different possible outcomes in the probe on websites like PredictIt.

Here's how PredictIt gamblers are betting on eight possible developments in the Mueller probe.

Since May 2017, special counsel Robert Mueller's probe into Russian interference in the 2016 election, and potential collaboration with Moscow to tilt the race in Trump's favor, has captivated the interest of observers in Washington and around the world.

The Mueller probe has also been a lucrative source of profit for some online gamblers who bet on the likelihood of different possible outcomes in the probe on websites like PredictIt.

PredictIt gamblers buy shares of a given bet, the value of which corresponds to the likelihood of a given event occurring. For example, shares of a formal Brexit agreement being reached by March 29, 2019 are trading at 26¢ a share, reflecting a 26% chance of the event happening by a certain date.

So far, 35 people, including eight people associated with the Trump campaign or administration and three Russian companies, have been charged in the investigation.

For online gamblers, betting on the Mueller probe is especially risky given the secrecy of the probe's inner workings. Mueller only speaks through official court filings and runs a leak-free investigation, often making it difficult to guess exactly what will happen next.

Some gamblers who placed bets on Trump ally Roger Stone being indicted for 67¢ a share made a profit on Friday, when Mueller charged Stone with one count of obstruction of justice, five counts of making false statements to investigators, and one count of witness tampering.

Here's how PredictIt gamblers are betting on eight possible developments in the Mueller probe: