Foreign-exchange traders’ messages on Facebook Inc. are being sought by European Union antitrust regulators as they expand a probe into alleged collusion between banks beyond work e-mails and instant messages, two people with knowledge of the case said. Banks have been asked to supply all communications between traders, including social media, said three people who didn’t want to be named because the EU’s requests are private. The EU suspects that some e-mails and online messages have been erased to destroy signs that traders were illegally swapping information, one of the people said. [Bloomberg]