Police are working to resolve the situation on the M25 Dartford Crossing, where they said two people remained “at height” on Tuesday morning.
One of the protesters on the bridge said he was “pretty cold” overnight but vowed to remain there until the government promised to end all new oil and gas.
The climate activists climbed to the top of the Queen Elizabeth II bridge in the early hours of Monday, flying a “Just Stop Oil” banner as they remained suspended by ropes.
Have you been affected by this story? Get in touch with zoe.tidman@independent
Commuters faced rush-hour delays as officers shut the crossing to deal with the protest.
Essex Police said the situation was still ongoing on Tuesday morning.
The bridge remained closed during rush-hour, with footage showing long traffic jams lining the area at 7am.
National Highways said there was around six miles in congestion in both directions approaching the crossing on Tuesday morning.
“There is no estimation for when the bridge may re-open at this stage,” it tweeted around 8.30am.
One of the activists shared a video of himself suspended on the bridge on Tuesday morning, with a view of the Thames below.
“We’ve just survived our first night up here. I was pretty cold. Didn’t sleep much – but I’m OK,” the civil engineer from London said.
He vowed to remain there “until the government makes a meaningful statement to cancel all new licenses and consents for oil and gas extraction”.
On Monday night, Chief Superintendent Simon Anslow from Essex Police said: “We understand how frustrating this situation is for people wanting to use the bridge and go about their business. Let me assure you we are doing all we can to resolve this situation quickly and safely. “
“It is a complex situation due to the height the people on the bridge are at.”
He said National Highways was responsible for the bridge and decided it was not safe to reopen it.
It comes amid a month of action from Just Stop Oil, which is calling for an end to all new oil and gas licenses.
The group blocked roads outside the Baron’s Court tube station in west London on Tuesday morning
Just Stop Oil has vowed to cause disruption every day in October in its campaign against fossil fuels.