(Bloomberg) -- Atlantia SpA investors faced dramatic losses as bond-price declines accelerated and the stock failed to open after the Italian government began the process of revoking its toll-road concession in the wake of a tragic bridge collapse.

The stock was poised to drop 23 percent to 18 euros, based on pre-market trading, from a closing price of 23.54 euros in Milan on Tuesday. Atlantia saw some of its bonds fall to their lowest levels ever, while highways unit Autostrade d’Italia, the company that operated the Genoa bridge, also endured a selloff in its debt.

Atlantia’s 1 billion euros of bonds due in July 2027 plunged below 88 cents on the euro on Thursday, the lowest since they were issued, according to data compiled by Bloomberg. The 700 million euros of notes due September 2029 issued by Autostrade fell below 88 cents on the euro, also a record. The cost of insuring Atlantia’s debt with credit-default swaps soared 59 basis points on Wednesday to 174, a near five-year high.

Atlantia, whose biggest owner is Italy’s Benetton family, confronted government officials on Thursday, saying political leaders’ comments that they would start the revocation process came prematurely, “without any verification of the material causes of the accident.”

Late Wednesday, Prime Minister Giuseppe Conte told reporters that the government will “start the procedure to revoke Autostrade’s license.” He said officials won’t wait for the outcome of a probe or a trial to take action.

The government may limit the license-withdrawal to the A10 highway that includes the bridge, not the entire toll-road network run by Autostrade, according to a Transport Ministry official who asked not to be named in line with internal policy.

The company says its contract requires Atlantia to be reimbursed if the concession is withdrawn, and said it will continue to support Autostrade “with the aim of protecting the interests of its shareholders and bondholders.”

If the Italian government revokes Autostrade’s highway operating license, the division’s creditors may have the option to accelerate repayment, Creditsights analysts wrote in a note on Wednesday, quoting the firm’s EMTN prospectus. The analysts changed their recommendation on the debt to ‘underperform.’

Morandi bridge, built in the 1960s, was part of a major artery connecting the Italian Riviera to the southern coast of France. It collapsed in a heavy rain on Tuesday, causing more than two dozen vehicles to drop to the railroad tracks about 150 feet below. At least 39 people died.

The disaster occurred during the height of Italy’s summer travel season, during the Ferragosto holiday. Most companies, including Atlantia, are shut down during the week. The bridge’s failure and accompanying loss of life has shocked Italians and led to questions about the safety of hundreds of aging bridges and tunnels.

Giovanni Castellucci, the chief executive officer of both Atlantia and Autostrade, has become a focus of anger over the tragedy, as politicians called for his removal. The Autostrade unit will hold an emergency board meeting early next week to evaluate the impact of the tragedy on its business and respond to government’s request, people familiar with the matter told Bloomberg News late Wednesday. The CEO has the support of the Benetton family and has no current plan to resign, one of the people said.

--With assistance from Chiara Remondini.

To contact the reporter on this story: Tommaso Ebhardt in Milan at tebhardt@bloomberg.net

To contact the editor responsible for this story: Anthony Palazzo at apalazzo@bloomberg.net

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