Carnival Triumph, which suffered an engine room fire leaving 4,000 passengers and crew adrift in the Gulf of Mexico four months ago, returned to service yesterday.

The cost of repairs and upgrades to the 14 year old ship hit $115 million, including six new entertainment areas.

The incident led to the cancellation of cruises and prompted Carnival Cruise Lines to embark on a $300 million “enhancement” of its 24-ship fleet to improve operating reliability.

The work also involves placing additional emergency diesel generators on the upper deck, and fire safety upgrades across all hips in the fleet.

Parent company Carnival Corporation is also conducting an operational review of its 10 brands and 101 ships at a cost of up to $700 million.

The Carnival Triumph accident in February made negative headlines around the world as passengers camped out on deck without hot food or working toilets.

Triumph’s troubles were the first in a string of problems suffered by the line this year.

Carnival Elation had to be escorted by a tugboat in March because of a malfunction in its steering system.

Carnival Dream lost power a few days later and some toilets stopped working in St. Maarten in the eastern Caribbean.

Technical difficulties were then reported on Carnival Legend affecting its sailing speed.