A cyberattack on the Washington Post compromised the email accounts of several journalists and was most likely the work of a foreign government, the Wall Street Journal reported on Sunday.

The Washington Post is investigating a cyber attack on the email accounts of some journalists, prompting the newspaper to beef up its online security.

The Post discovered the “possible targeted” hack of its email system last Thursday, prompting the newspaper to reset login credentials for all its employees on Friday, Washington Post Executive Editor Matt Murray said in a memo Sunday to employees.