The Federal Election Commission has launched a preliminary investigation into whether Russian entities gave illegal contributions to the National Rifle Association that were intended to benefit the Trump campaign during the 2016 presidential election, according to people who were notified of the probe.

The inquiry stems in part from a complaint from a liberal advocacy group, the American Democracy Legal Fund, which asked the FEC to look into media reports about links between the rifle association and Russian entities, including a banker with close ties to Russian President Vladimir Putin.

A spokesman for the NRA and its lobbying arm, the Institute for Legislative Action, which together contributed $30 million to Trump’s presidential campaign, declined to comment on the FEC’s probe.