At 10am, officers, detectives and search teams taking part in the operation, codenamed Operation Symphony, entered six yards across four counties - including A1 Group at Silver Birches in Highland Ave, Wokingham.
Police may be at some sites for several days to seize business records for forensic examination and check stock.
Thames Valley Police (TVP) said metal thefts are costing the UK £770million a year, plus the threat to people reliant on electricity or telephone lines, and the emotional suffering where memorial plaques have been stolen. In Bracknell, St Margaret Clitherow Church in Birch Hill has been demolished after its copper roofing was repeatedly stolen.
Detective Chief Superintendent Brendan O'Dowda, head of TVP's force intelligence unit and specialist operations, was in charge of the operation. He said: "You just wouldn't believe the lengths that some of those thieves will go to to get some cash. They will steal crematorium plaques and plaques from war memorials.
"This is not a victimless crime."
The raids followed months of joint working between TVP, neighbouring forces, British Transport Police, local authorities, the Environment Agency and the British Recycling Agency.
The News has attempted to contact A1 Group but has not yet had a response.