The European Commission suspended its carbon trading scheme on Wednesday after it was attacked by computer hackers.
Carbon permits worth worth 6.7 million euros are missing.
France, the Czech Republic, Greece, Estonia and Poland closed their carbon trading registries earlier on Wednesday, joining Austria.
The commission said the suspension of most transactions would last until at least 26 January and only the allocation and surrender of carbon allowances would be allowed.
The problems are not the first for the EU carbon trading scheme.
In the past two years, it has had to contend with the re-sale of used carbon credits, a phishing scam in February last year and continuing VAT fraud.