Switzerland’s stock exchange SIX is investigating specialty chemicals producer Clariant on grounds it may have breached the market’s ad hoc disclosure requirements when launching its bid to acquire Huntsman in May 2017.

SIX said it is basing the investigation on Clariant’s press release regarding the announcement of the merger agreement dated 22 May 2017. The probe is due to continue for an “indefinite period,” and the exchange said it will “provide no further information in the meantime.‍​”

Rejecting the SIX concerns, Clariant said it believes it upheld all requirements. “From Clariant’s point of view, the ad hoc publicity requirements ... were fully respected,” the Muttenz-based group said in a statement emailed to news agencies on Jan. 11.

Clariant said it had involved Swiss Radio and Television (SRF) in the announcement prior to the general disclosure in order to provide the public with background information on the transaction.

“The SRF depended on early involvement in order to be able to fulfill its role. As part of this involvement, a legally binding confidentiality agreement was signed,” Clariant said. “This agreement included the obligation to only air the report after the announcement of the planned merger.”

It was unclear whether SIX was acting on its own accord or had received a complaint from a third party. Clariant is still struggling with its activist investor White Tale, the acquisition vehicle of two US-managed hedge funds based in the Cayman Islands.

Opposition to the merger by White Tale, which by that time had accumulated 20% of Clariant’s capital, led to the transaction being scuppered in late October 2017. The chemical producer and the investor are still at loggerheads over White Tale’s request for an independent strategic review and three seats on Clariant’s board of directors.