Activist investor Elliott Investment Management LP has built a sizable position in Canadian National Railway Co., ratcheting up pressure on the company to improve its results, according to people familiar with the matter. 

The Florida-based hedge fund has held discussions with Canadian National in recent weeks, ahead of the Tuesday’s surprise announcement that Chief Executive Officer Jean-Jacques Ruest would step down in early 2022, the people said, asking not to be identified because the matter is private. 

The involvement of Paul Singer’s Elliott opens a new front in the squeeze on Canadian National, which is in the midst of a proxy contest with billionaire Chris Hohn’s TCI Fund Management Ltd. 

TCI has criticized the Montreal-based railway for underperforming its peers under Ruest and has been pressing for industry veteran Jim Vena to take over as CEO. Elliott is also supportive of Vena’s appointment, the people said.

It’s unclear how many shares Elliott owns and the nature of its discussions with CN. The Wall Street Journal first reported on Elliott’s stake on Wednesday. 

“CN’s board is open-minded and will consider all qualified and interested candidates,” the railway said in a statement, without confirming Elliott’s stake. A representative for Elliott declined to comment. 

TCI has also nominated four directors to the railway’s board. Shareholders will have a chance to vote on the matter on March 22. 

Canadian National gained as much as 6.6 per cent on Wednesday in Toronto after the announcement of Ruest’s departure and a strong third-quarter earnings report, closing at a record $161.53.