Twitter‘s board is considering major change, following news that former chief executive officer Dick Costolo is planning to exit the company.

The company is reportedly looking for a permanent CEO in order to bring more diversity to the board, which can be brought by someone belonging to minority group or from those having experience in advertising or e-commerce fields.

Former CEOs including Ev Williams and Costolo, and interim CEO Jack Dorsey are expected to remain on the board, Bloomberg reported, as it could be difficult for a new person to run the company.

Jack Dorsey became the interim CEO after Costolo stepped down from the position in July.

Twitter is going through a tough time as the number of monthly average users grew at a slow pace in the second quarter this year, which was recorded to be the lowest since it went public in 2013.

Dorsey could not be ruled out of becoming the permanent CEO of the company, but according to reports, other front-runners include Flipboard CEO Mike McCue, Instagram founder Kevin Systrom, and Medium CEO Evan Williams, reported SunTrust Robinson Humphrey.