Work has stopped at 100 sites around Scotland, where they carry out groundwork and civil engineering for house builders.
Company directors are reported to have already left the firm, which is based in Bothwell, Lanarkshire, after telling members of the 700-strong workforce that there were severe cashflow problems.
A company source said: “We have currently ceased trading and are waiting for the banks to appoint an administrator.
“There is nothing more to say and a formal statement will be issued shortly”
The firm’s problems are a blow to the Scottish civil engineering industry, which has seen several contractors collapse over the last two years, but few of the size of Harte, which turned over more than £100m.
Construction union UCATT said it has “received a substantial number of calls” from workers concerned about the future of the firm.
The company has being carrying out work for house builders in Scotland for more than 40 years and is understood to have lost the support of its bankers.
Local MPs have called for meetings with Harte directors but have been told nobody was available.
Ucatt regional secretary Harry Frew said: “It’s extremely disappointing to hear that WJ Harte is facing such difficulties threatening hundreds of jobs.
“We hope that a buyer can be found and jobs preserved. UCATT is seeking a meeting with the administrators to establish what the future holds for our members.
“The impact of these potential job losses across central Scotland will be a major blow to workers and their families. It is imperative that everything is done to safeguard these valuable construction jobs.”