The police have declared a major incident over a bonfire in south Belfast that is due to be lit on Friday as part of annual Twelfth events across Northern Ireland.

Belfast City Council have requested the police assist contractors to dismantle the bonfire before it is lit.

There are concerns that the power supply to Belfast City Hospital and the Royal Victoria Hospital would be put at risk because the bonfire lies near a major electricity substation.

On Thursday afternoon, bonfire builders voluntarily removed tiers of pallets from the top of the bonfire and told BBC News NI the action was an “olive branch” to those concerned.

The Police Service of Northern Ireland (PSNI) said no decision had been taken on assisting the removal of the bonfire and they continued to work with agencies and community representatives on this matter.

Bonfires are lit as part of Eleventh night celebrations in some unionist areas of Northern Ireland, to usher in the Twelfth of July, the main date in the parading season.

The Twelfth commemorates the Battle of the Boyne in 1690 when the Protestant King William III – also known as King Billy and William of Orange – defeated Catholic King James II.

Bonfires were lit on 11 July to welcome – and guide – William.

There are separate concerns about the presence of asbestos at the bonfire site which is between the Donegall Road and the Westlink and the council voted to write to the environment minister to act immediately to have it removed.

The Deputy First Minister and DUP MLA, Emma Little-Pengelly, said: “No one wants anyone to be hurt or for there to be any risks to health or wellbeing”.

On Facebook she said those involved in the bonfire had engaged for “some time” on “size and other mitigations” and she believed that would continue.

Earlier, Sinn Féin MLA Pat Sheehan told BBC’s Good Morning Ulster programme on Thursday that the police “have a responsibility” in the situation.

He said the issue had only been brought into the public domain because it is “the first time a bonfire has been held in this site”.

He also called on action from the landowner and the Northern Ireland Environment Agency (NIEA) regarding the asbestos.

Sheehan also called on unionist politicians to “show leadership” and said Emma Little Pengelly “should be out today calling for that bonfire to be dismantled. Where is her leadership?”

The PSNI appears to have been put between a rock and a hard place here by a political decision at the 11th hour.

One of its considerations is most certainly: Would any operation trigger disorder which could spread to other areas?

Just 36 hours ago, the PSNI felt the mood music going into the 12th of July was pretty positive.

Now we have a significant bonfire row which has escalated tensions.

We saw evidence last night of how the local community has reacted to the prospect of a police operation.

Site entrances were blocked, a protest took place on the road, people were in an around the bonfire, and there is also a risk it could be lit early if any operation is mobilised.

Residents of the Village area of Belfast, where the bonfire is situated, said the bonfire means “everything”.

“This bonfire has been going for all of our generations… and we want our next generations to know our culture. This isn’t to get up anybody’s nose.

“The children of this area have been collecting for the bonfire since Christmas time.”

Billy Garrett, another resident, said there was “a lot of frustration”.

“It’s just another attack on our culture and our traditions. We don’t see any harm in what we’re doing here, especially in the Village area of south Belfast. It’s just knocking the heart out of everyone,” he told BBC News NI.

He said the organisers of the bonfire site had been making sure it was safe since September last year.

“They’ve went through all the proper people to make sure it is safe for everyone in the community.”

Loyalist activist Jamie Bryson planned to take legal action to stop the bonfire being dismantled and has questioned the decision-making process behind the vote.

However, the council rejected claims that the decision to dismantle the bonfire breached legal guidelines and said the move was part of its “emergency” decision-making processes.

It also said it was in line with the rules of council, those cases on which an “inability to immediately implement a decision would result in a breach of statutory or contractual duty”.

Belfast Health Trust said the bonfire was near a substation that supplies both hospitals.

Northern Ireland Electricity (NIE) said it had expressed concerns over the bonfire’s “proximity to the substation causing potential risk to critical infrastructure and power outages”.

The trust said it had contingency measures including back-up generators and it was confident there was no need to cancel any planned treatments or procedures.

The NIEA said it was first alerted to the issues of asbestos near the bonfire on 16 May and had been engaging with the landowner and the city council regularly since then.

An inspection was carried out and the NIEA said if the asbestos was not cleared by 11 July, “mitigating measures” would need to be put in place.

The landowners, Boron Developments, bought the site in the summer of 2017 and were made aware of asbestos at that time.

Boron Developments have said it engaged a waste management company to remove the asbestos but the company needed “no personnel” on the site in order to complete the removal of asbestos.

Due to people “bringing in materials and building the bonfire” the company told the landowners it could not complete its work.

Belfast City Council said while the lands at the site remained “the responsibility of the landowner” the council and the Northern Ireland Environment Agency (NIEA) were “working together in relation to this site”.

The Department of Agriculture, Environment and Rural Affairs said it had put in place mitigations “over the past week including the further covering of the asbestos containing material, the use of fire-retardant material and the erection of additional fencing”.