No badge, no gun, no handcuffs — and no clothes.

None of that stopped an off-duty Swedish police officer from making an arrest last week after recognizing the man sitting next to him in a sauna as a fugitive, according to local news reports.

“It’s easier to take action when you have your colleagues with you, and all your tools and equipment,” Christoffer Bohman, deputy police chief in the district of Rinkeby in Stockholm, told the Swedish state broadcaster SVT, according to the news site The Local.

“This was as stripped-down as it gets — in more ways than one,” he added.

Mr. Bohman did not identify the officer or the fugitive, who The Local said had gone on the run after being sentenced to prison for a drug-related crime. The arrest last Friday was potentially dangerous because the fugitive had also been convicted of attempting to assault a public servant, The Local reported, without elaborating.

Mr. Bohman congratulated the officer in a Facebook post for keeping a cool head even as the situation heated up.