The chairman of the US senate intelligence committee has said the panel is continuing to investigate possible collusion between Russia and associates of Donald Trump’s election campaign – but has not reached a conclusion yet.

Senator Richard Burr, a North Carolina Republican, gave an update on the committee’s investigation into Russian interference in the 2016 presidential election.

He was joined by the committee’s top Democrat, senator Mark Warner of Virginia.

Mr Burr said the committee has interviewed more than 100 witnesses as part of its investigation and that more work still needs to be done.

He said: “The issue of collusion is still open.”

Mr Warner said there is a “large consensus” that Russians hacked into political files and released that information in an effort to influence the election.

He said the Russian effort to sway the election also involved attempts to test the vulnerabilities of 21 states’ election systems.

Mr Burr said no vote counts were altered.

The committee is one of several that are investigating Russian interference in the election and potential collusion between Russia and associates of the Trump campaign.