Carillion, which is involved in major infrastructure projects for the British and other governments, has been fighting for its survival after costly contract delays and a downturn in new business. In November it issued its third profit warning in five months.
The investigation by the markets watchdog concerns "the timeliness and content of announcements made by Carillion between Dec. 7 2016 and July 10 2017," the company said in a brief statement to the London Stock Exchange.
Carillion said it was cooperating fully with the FCA.
In the period under review, Carillion released a full year trading update, its 2016 results, an annual general meeting statement and a 2017 first-half trading update. Its shares fell more than 54 percent over the seven months.
The company announced on July 10 it would undertake a review of its business, suspended its dividend, announced divestments and said it expected overall performance to be below management's previous expectations.
Carillion also said then that Richard Howson would step down as chief executive and named Keith Cochrane as interim CEO.
Analysts estimate the company is also grappling with debt including provisions, pensions and accounts payable of about 1.5 billion pounds.
Carillion's shares were down 3 percent at 17.4 pence by 0835 GMT, making up some lost ground after falling more than 8 percent. They have lost 90 percent of their value since the profit warning on July 10.
Carillion's market capitalisation stands at about 70 million pounds, according to Thomson Reuters data.
Carillion and FCA declined to provide any additional details on the investigation.
Carillion last month moved forward the start date for new chief executive Andrew Davies forward to Jan. 22 from April 2.
Davies, head of family-owned builder Wates Group and formerly with defence company BAE Systems, will replace interim CEO Cochrane.
(Reporting by Arathy S Nair in Bengaluru; editing by Jason Neely/Keith Weir)
By Arathy S Nair