The huge Warner Bros Studios fire was on the set of the new comedy show Avenue 5, the Watford Observer can confirm.
A source, who asked not to be named, told al Observer before today the fire was on the HBO series set, set aboard a space touring ship and played by Hugh Laurie.
Another source reported at the Observer that a model of a space cruise ship inside P Stage on the studios site had caught fire.
Tonight, the producer of Avenue 5, the creator of the Armando Iannucci series, said: "On behalf of the entire cast and crew of Avenue 5, I want to thank the firefighters who worked tirelessly all night to keep everyone and all safe.
"I send my thoughts to the residents of the area who have been disturbed by the night's events. It was a beautiful set but everyone's safety is the main priority. The season is almost complete and everyone is determined to continue."
A fire group in South Way today
Avenue 5 is the next American science fiction television series created by The Thick of It producer Armando Iannucci, which will premiere on HBO.
It stars Blackadder and House Hugh Laurie as Ryan Clark, captain of the spacecraft Avenue 5.
Firefighters were called to the movie studios at 11:30 pm last night, but the call was intensified and another 13 firefighters from the other side of Hertfordshire participated to help put out the fire .
Fortunately, there were no reports of injuries and the set was not used at that time.
The scene in the Hunton Bridge today
It is believed that the fire has always been "under control" but three members of the crew arrived this morning while the crews pumped water from a nearby canal at Hunton Bridge to help cope with the fire .
Hunton Hill Bridge and South Way were reopened after being closed for most of the day to allow firefighters to connect a pipe between the canal and the studios.
At 14.50, the Hertfordshire County Council confirmed that the fire was out but several emergency vehicles remain in place.
HBO said: "The Warner Bros. Studios Leavesden fire hit one of the HBO sets" Avenue 5. The production continues as producers and writers evaluate the best plan to complete the filming of the last two episodes of the series: we praise Armando Iannucci for the firefighters who brought this situation to a safe conclusion. "
Warner Bros added: "The Chief Fire Officer has confirmed that the fire that occurred in one of our sound stages, used by the television production Avenue 5, has been completely extinguished.
"Our main concern is always the safety of people and we would like to thank the Hertfordshire Fire and Rescue Services for all their hard work in containing the situation. All productions have been able to continue to work and the Studio Tour does not was influenced. "