BRUSSELS, Nov 22 (Reuters) - EU antitrust regulators on

Friday closed a four-year long investigation into Apple's ( AAPL )

rules for competing e-book and audiobook apps

developers after the complainant withdrew its complaint against

the iPhone maker.

"The closure of an investigation is not a finding that the

conduct in question complies with EU competition rules," the

European Commission, which acts as the EU antitrust enforcer,

said. It did not name the complainant.

It said it would continue to monitor business practices in

the European tech sector, including those of Apple ( AAPL ), both under

the Digital Markets Act and competition rules.