HS2 campaigners involved in an underground protest in central London have said “liquid mud” is pouring into one of their tunnels.

Veteran environmental campaigner Swampy, who is one of at least five people in the 100ft network of tunnels dug under Euston Square Gardens, said on Friday that the situation is “not safe” after it rained overnight.

It comes after officials warned that the protesters are at risk of suffocation or drowning.

The HS2 Rebellion campaigners involved in the protest claim the small green space near Euston Station will be built over with a temporary taxi rank before being sold to developers as part of plans for the high-speed railway.

The Metropolitan Police said two arrests had been made on Friday under the Trade Union and Labour Relations (Consolidation Act).

Five others were arrested at the scene on Thursday, three for allegedly breaching Covid regulations.

At least five people remain in the network of tunnels, which took months to build.

In a video issued by HS2 Rebellion, Swampy, real name Daniel Hooper, said: “There was liquid mud coming through the wall last night, the rain stopped and we informed them (bailiffs) of this problem.

“They said they were going to pump the water out, the rain has now stopped and loads more liquid mud is coming down now.”

Mr Hooper added: “This is not safe, there’s not enough room for people to get out quickly from this tunnel.”

He went on to claim water was being pumped into the tunnels to force them out.

An HS2 spokesman has dismissed these claims as “untrue”, saying no water or mud has been pumped into the tunnels.

Protester Larch Maxey, 48, who is also situated in one of the tunnels, said there had been five collapses overnight.

The National Eviction Team previously warned the “very dangerous” tunnels could collapse.