David Teoh, chairman of Australia-listed Tuas Ltd.Getty ImagesSingapore-listed Keppel Ltd. is letting the proposed sale of mobile carrier, M1, to Australian billionaire David Teoh lapse on Thursday after government regulators halted the evaluation of the transaction this week as the self-made tycoon’s Simba Telecom was found to have breached regulations.The Infocomm Media Development Authority of Singapore (IMDA) said it has suspended its review of the acquisition after it learned that Simba may have been using unauthorized radio frequency bands, according to a stock exchange filing by Tuas Ltd. on Monday. That imperils the S$1.4 billion ($1.1 billion) deal, which was first announced by Teoh’s Australia-listed Tuas in August.“Simba is fully co-operating with the IMDA,” The company said in the statement. “The board of Tuas will also be reviewing the circumstances concerning the alleged unauthorised use of [radio frequency] spectrum.” Tuas shares plunged more than 60% on Monday in Sydney trading, before climbing about 17% today.M1’s parent, Keppel said in a separate statement on Monday that the sale and purchase agreement between M1 and Simba will lapse after reaching its long-stop date on May 21. Keppel also said it will begin restructuring M1, focusing on rightsizing the business and cutting costs.“Even as we undertake this efficiency drive at M1, we believe that the telecommunication industry in Singapore is in dire need of and will benefit from consolidation,” Loh Chin Hua, CEO of Keppel said in the statement.“Keppel remains open to opportunities for divestment”.MORE FOR YOUIn August last year, Keppel agreed to sell its 83.9% stake in M1—Singapore’s third largest mobile carrier—to Simba Telecom for nearly S$1 billion in cash. Under the proposed deal, Keppel would retain M1’s information and communications technology businesses, which complement the conglomerate’s connectivity operations, including data centers and subsea cables.With a real-time net worth of $2 billion, Teoh is among the wealthiest in Australia. The Australian citizen of Malaysian descent, is the founder and former executive chairman of TPG Telecom. Tuas was spun off as a separately listed company after its parent, TPG Telecom, merged with Vodafone Australia in March 2020.