SINGAPORE (Reuters) – BP

has terminated four trading and operations staff responsible for Chinese crude oil sales as a result of an internal investigation into trades with Singapore’s Hontop Energy, three people familiar with the matter said.

The decision was made this week, the people said. The staff had been placed on leave in early July while BP conducted its probe.

The staff worked in crude trading and operations roles in Singapore and Shanghai, they said.

The improper use of the WeChat messaging platform as a tool for commercial discussions with counterparties was cited as a factor behind the terminations, one person said.

BP said the company does not comment on personnel matters or on its WeChat usage policy.

BP trading staff, including some of those terminated this week, were named in a court document filed by Malaysian lender CIMB as part of the bank’s request to the Singapore High