BRUSSELS — The European Union today ordered U.S. biotech giant Illumina to undo its $7.1 billion purchase of cancer-screening company Grail because it closed the deal without approval of regulators in the 27-nation bloc.

The EU already slapped a $475 million fine on Illumina over the summer for jumping the gun on the acquisition without its consent. Now, the order to unwind the deal “restores competition in the development of early cancer detection tests,” EU antitrust Commissioner Didier Reynders said.

“By ordering Illumina to restore Grail’s independence, we ensure a level playing field in this crucial market to the ultimate benefit of European consumers,” he said.

Illumina said it is reviewing the order to sell Grail. The company also has previously asked the EU’s highest court to rule on its challenge to the bloc’s ability to review the merger.

Allowing the deal to stand would have undermined the credibility of EU regulators. Companies almost invariably play by the rules and wait to complete an acquisition or merger until antitrust authorities have cleared it, according to the European Commission, the EU’s executive arm and top antitrust enforcer.

Illumina announced the acquisition of Grail in 2020, but the commission said the company broke EU merger rules by completing the deal without its consent. The commission prohibited the deal in September 2022.

The EU accused Illumina and Grail of knowingly and deliberately merging before getting clearance in what amounted to a vital infringement of the rules.

Illumina must “restore the situation prevailing before” the acquisition, regulators said, and how Illumina divests itself of Grail also needs EU approval.

Regulators worldwide have targeted the deal. The Federal Trade Commission ordered Illumina to sell Grail earlier this year after finding the merger would “stifle competition and innovation in the U.S. market for life-saving cancer tests.”

The EU said the acquisition would squeeze out competitors and give Illumina too dominant of a position in the market.

San Diego-based Illumina is a major supplier of next-generation sequencing systems for genetic and genomic analysis, while Grail is a health company developing blood tests to try to catch cancer early.