Thieves have struck again at a Walton metal treatment facility stealing a fifth bag contaminated with cyanide.

Surrey Police say the public should not touch the bag which was stolen from JM Wozny Plating Ltd metal treatment plant on the North Weylands industrial estate between 10am on Sunday and 8.30am yesterday.

Burglars broke into the facility by making a hole in a plastic roof and then stealing the white bag containing potassium cyanide along with thousands of pounds worth of silver anodes - instruments used in silver plating.

The cyanide chemical is not believed to be dangerous if it is in a large open area, but is potentially fatal if it enters the body by touch or mouth.

Thieves stole four bags containing potassium cyanide in an earlier break in at the facility on July 29 at around 9.15pm.

They used a vehicle to smash into the front of the premises and grabbed the bags which still have not been recovered.

A JM Wozny spokesman said: "A day and a half after the first robbery someone tried to break in again.

"It was at night and they drove into the front of our premises, but we think they realised someone was inside and they decided to leave.

"With security, everything that is recommended by the police the company will do to protect the business.

"We have already secured the roof where these thieves gained entry."

He said the company would definitely not relocate to new premises.

"Just because someone terrorises or burgles your house it doesn't mean that you move," he said.

"The situation is the same with us. They are not going to win. Never give in to criminals, terrorists or anyone."

The bags are made of a white canvas material and are roughly 30cm by 30cm. They are split into two sections, with a metal rod in each of these two sections.

Investigating officer Detective Constable Bex Humber said: "Again we are concerned the offenders were targeting precious metals and did not know what was inside this bag and may discard it.

"We would urge anyone who sees bags matching this description they should not touch or approach them but call 999 immediately."

Anyone with information is asked to call D Con Humber at Surrey Police on 0845 125 2222 or Crimestoppers on 0800 555 111.