British Telecom's shares plunged by nearly 21% as of 2:25 p.m. ET Jan. 24, wiping £7.8 billion off its value, after the company disclosed accounting errors at its Italian business, Reuters reported.

An investigation into accounting practices at BT Italy started in October 2016, and has reportedly led to a write down of £530 million, a sum far higher than the £145 million initially announced last year.

BT now expects operating profit for 2016/17 to be £7.6 billion, compared to previous guidance of £7.9 billion.

The British communications giant said it had suspended a number of BT Italy's senior management team members who have reportedly left the business. A new CEO of BT Italy will take charge Feb. 1.

The company said the new chief executive will review the local management team and work to improve the governance, compliance and financial safeguards of its Italian business.