WASHINGTON (AFP) - A data breach of US government workers allowed hackers to access sensitive information including security clearances of the workers and contractors, the Washington Post reported Friday.

The report said investigators are looking at two separate attacks, widely believed to be from China, accessing government employee records in a database at the Office of Personnel Management.

The database "is very sensitive and it has lots of interfaces to it," a US official told the newspaper on condition of anonymity.

The report said the database may contain files on some CIA employees.

"That's the open question - whether it's going to hit CIA folks," a second official was quoted as saying.

"It would be a huge deal. They could start unmasking identities."

The database contains personal information on employees including their financial histories, investment records, family data, contacts with foreigners and names of neighbors and friends, according to the report.

Earlier this week, a public employees union said the suspected Chinese hackers obtained sensitive information on all federal employees.

The US government last week admitted that data linked to at least four million current and former federal employees was hacked.

The hack of the Office of Personnel Management included records on 750,000 Department of Defence civilian personnel.