Constantine premiere
Matt Ryan as John Constantine in the NBC show NBC

NBC's Constantine season 1 is trimmed to 13 episodes, and the show's future is uncertain.

The cast and crew of the series were informed that the series will halt production after completing production on the initial 13-episode order, deadline reported.

Constantine will continue to air in its 10pm Friday time slot for the rest of the episodes.

In response to the series' uncertain future, fans have started an online petition to save the show.

Save Constantine petition is on a mission to gather 100,000 signatures from fellow supporters, demanding the NBC officials to give the show a second chance.

The petition website says: "NBC has not ordered a full season for Constantine despite it's above average initial ratings and increasing quality and fanbase. The show is doing well for it's circumstances: it has one of the worst time slots imaginable, 10pm on Friday nights."

The petition also has support from a Twitter campaign, advocating the show's renewal.

Several tweets on #SaveConstantine from the show's writers, producers, and fans, including celebrities like William Shatner are keeping the show's hopes alive.

Showrunner Daniel Cerone also spoke against the cancellation rumours in a flurry of tweets.

Here are some of his tweets:

The show is based on the wildly popular DC Comics series "Hellblazer." Matt Ryan stars as John Constantine, who is a demon hunter and master of the occult.

NBC's Constantine airs at 10pm on Fridays.