Jed Mercurio left viewers of the BBC police drama wondering whether he had just hinted at a season seven when he posted a photo of the AC-12 banner with the caption: "Carry the fire."
The phrase referred to the final scene that Superintendent Ted Hastings (Adrian Dunbar) spoke in during Sunday night's season finale, where he admitted to his rival DCI Patricia Carmichael (Anna Maxwell Martin) that he had revealed to OCG member Lee Banks that there was an undercover officer in their midst, leading to John Corbett's death.
Asked what she was supposed to do with the information, Hastings urged her: "That's entirely up to you, but whatever you do, you do it because you care about truth and accountability.
"You do it because you carry the fire."
Mercurio made it clear he wasn't going to give away anything else for the moment by turning off comments on his tweet, leaving viewers to speculate over whether new episodes could be on the way.
Another responded: "I’m certain (in a hope against hope kind of way) that this is a hint that there’s either a new series or a denouement episode to finish tie up the ‘ends’."
Someone else added: "I take this as a new series is coming!"
Plenty of Line of Duty fans will be hoping for another chance at finding out who the orchestrator of police corruption is after a big reveal that many branded "disappointing".
The end of season six saw jailed detective Ian Buckells named as H, or the Fourth Man, who had been at the head of links between the OCG and corrupt officers.
Described by AC-12 as a "blundering fool", viewers agreed that he was an unlikely criminal mastermind and said they felt underwhelmed by the ending.
But the show's stars have already said they would love to come back for another run if possible.
Martin Compston, who plays DI Steve Arnott, said: "There’s always potential for it to go on. We could always start a new case.
"There’s always corruption out there, as (Mercurio) would say, but at the same time where there’s a lot of big questions getting answered in this series, there’s always loose ends.
"He always leaves something dangling for you, whether that’s just a look from Adrian at the end of a series, which might mean something, might not mean something…"
Adrian Dunbar, who plays Superintendent Ted Hastings, added: "I mean we’ve all to get on to Jed and say, 'We’ve got to do one that’s not like when we were in lockdown.'"
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