BARCELONA, Spain — Nine men were arrested on Tuesday in a series of early morning raids in and around Barcelona, Spain, in connection with the March 2016 terrorist attacks in Brussels.

The arrests were a reminder that an international investigation continued 13 months after the attacks, which struck the Brussels airport and a subway station, killing 32 people, and three bombers.

Jordi Jané, the home affairs minister for the Catalonia region, said the arrests were made “in connection with the terrorist attacks that occurred in Belgium” last March, but he added that the precise role of the men was still being investigated. The suspects were believed to have links with “an organized group associated with jihadi terrorism,” he said.