Construction company Interserve (LON:IRV) saw shares tumble over 30 percent on Thursday, after a slow third quarter led to a profit warning.

Interserve said it now expected profits for the second hald of the year to be about half of those in the same period last year, adding that there was be a “realistic prospect” it will breach its banking covenants.

“We now believe there is a realistic prospect that we will not meet the net debt to ebitda test contained in our financial covenants for 31 December 2017,” Interserve said on Thursday, causing the stock to plunge over 30 percent in early morning trading.

The stock has now fallen by over 80 percent this year, after the company issued a first profit warning last month.

However, chief executive Debbie White remained confident about the group’s potential, saying on a conference call with analysts that there was “considerable potential for business improvement across the company”.

Interserve shares are currently trading down 25.56 percent at 67.00 (1501GMT).