Color Line is fighting the biggest ever Norwegian fine for breaching sulphur emissions rules.
The Sysla website said the Norwegian Maritime Directorate slapped a penalty of NOK 600,000 ($77,650) on the company for readings from its 75,000-gt ro-pax Color Magic (built 2005).
Three higher-than-permitted readings were detected by Danish authorities last year in the Great Belt.
This caused Norway to make a spot check in Oslo, examining logbooks.
