Dow Chemical Co. and DuPont Co. were told by the European Commission to provide missing data about their proposed merger, threatening to delay the regulator’s probe into their plans to create the world’s biggest chemical company.

Technology advances and customer demand are driving mid-market agriculture deals. Agco Corp. (NYSE:AGCO) is acquiring Cimbria Holdings Ltd.; Advent said it will purchase Viakem; and Lariat Partners invested in Willowood USA.

The EU suspended its Jan. 11 deadline last week, barely a month after it opened an in-depth investigation into the transaction, citing concerns that the combination may reduce competition for crop protection, seeds and some petrochemicals.

"This procedure in merger investigations is activated if the parties do not provide an important piece of information that the commission has requested," Ricardo Cardoso, a spokesman for the Brussels-based commission, said in an e-mail. "Once the missing information is supplied by the parties, the clock is re-started and the deadline for the commission’s decision is then adjusted accordingly."

Regulators twice stopped the clock on their review of Halliburton Co.’s bid to buy oil-services rival Baker Hughes Inc. earlier in 2016, saying they needed more information from the companies. The firms abandoned the deal in May as the companies struggled to overcome antitrust concerns from the U.S., the EU and other regulators. The EU’s move "does not change our timing expectations," Dow and DuPont representatives both said in separate e-mails.

The Dow-DuPont combination is the first of a trio of big agricultural products deals to face EU scrutiny. EU lawmakers and environmental campaigners have been calling on EU antitrust chief Margrethe Vestager to block Bayer AG’s bid for Monsanto Co. (NYSE: MON) and  China National Chemical Corp. is yet to seek EU approval for its acquisition of Switzerland’s Syngenta AG.

--Additional reporting by Mergers & Acquisitions' Demitri Diakantonis