European Union antitrust authorities' probes into a planned $50 million merger of Switzerland's Holcim Ltd. (OTCMKTS: HCMLY) and France's Lafarge SA (EPA: LG) that would form the world's largest cement maker are slowing the deal's progress.

Holcim said Wednesday it has set up a divestment committee for its merger with Lafarge and has received “considerable” interest from prospective buyers in other countries, including “companies from the construction industry” and “financial investors such as private-equity companies,” the Wall Street Journal reported. Holcim also said the asset sales wouldn’t happen until regulatory approval is secured for the merger.

The companies announced their merger plans in April, pledging to set aside $6.8 billion in annual revenue to fight competition concerns. EU antitrust chief Joaquin Almunia said in April his agency will probe the merger extensively, Reuters reported.

The asset sales are a hurdle to regulatory approval because the cement industry is already highly concentrated and giant cement producers are among the buyers. CVC Capital Partners Ltd. and KKR & Co. are among those considering bids, Bloomberg reported.

Also, private-equity investors may be wary of the sector because an April antitrust judgment holds private-equity firms responsible for cartel fines incurred by firms in their portfolios.

In an acquisition separate from the Lafarge merger, the European Commission cleared Holcim to acquire Cemex West in Germany, the company announced Thursday. In Spain, Cemex (NYSE: CX) and Holcim plan to combine their operations in cement, ready-mix concrete and aggregates and are waiting for regulatory approval from the European Commission.