High winds overnight have caused extensive damage to power lines across the east of England and south east, interrupting electricity supplies to about 21,000 customers.

That number is likely to rise this morning as more damage is reported, and includes 20,000 properties in the south east and 1,400 in the east of England.

UK Power Networks engineers worked through the night and will continue today, moving from job to job to repair the damage and restore power as quickly as is safely possible. It will be carrying out helicopter patrols to check overhead power lines.

Customer service staff and volunteers from the British Red Cross, which works in partnership with UK Power Networks, will also be on site helping people in the worst affected areas.

Since midnight, advisors have spoken to about 300 people to keep them updated as repair work progressed. Customers can report any power cuts and damaged lines on free helplines: in the south east call 0800 783 8866 and in the east of England call 0800 783 8838.

You can also see ukpowernetworks.co.uk and follow the company on twitter for updates. Anyone spotting a damaged power line is urged to report it, but please stay well clear.

A spokesman for UK Power Networks said: “If you call during a major incident you are likely to hear an automatic message which recognises the area you are calling from and gives information about known faults in that area. You have an option to speak to an advisor too.

“UK Power Networks made careful and robust preparations for the stormy weather. Senior staff are in close contact with the Met Office. The electricity network is built to be resilient but extreme weather can see overhead power lines damaged by tree branches and wind-borne debris.

“We activated the early stages of our emergency plans on Friday and brought in additional staff covering engineering, technical and call centre roles.”

In the event of a power cut you can:

• Call the UK Power Networks free power cut helpline for the area or follow the firm on twitter

• Visit the website and twitter for updates on progress

• Keep a torch close to hand and if using candles, use them safely

• Stay warm by staying in one room, or even in bed

• Keep an eye on elderly or ill people living nearby

• Take care if you go out tonight as street lights may also be off supply

• Switch off most electrical equipment.