Shares in construction firm Costain have tumbled nearly 40% after it warned it had been hit contract delays.
It said it projects affected include the M6 Smart Motorway, Preston distributor road and HS2 Southern Section main works.
The M4 Corridor around Newport project was cancelled by the Welsh Government earlier this month, it added.
That means its revenue for 2019 will be lower than previously anticipated and underlying operating profit for the full year is expected to be in the range of £38m to £42m.
Alex Vaughan, chief executive officer, said: "Despite delays to the timing of certain contract start dates and new awards, our markets are strong, as evidenced by the breadth of our new contract awards in the first half.
"We have a strong balance sheet, profitable operations and a broad range of capabilities to support the growth of the business. Costain is well placed to secure the opportunities ahead of us."