Ann: Suspension from Official Quotation , page-10

Basically, listing rules require management to notify shareholders of any material developments as soon as they become aware of that info.

If there's a gap between when management are aware and when the information can be adequately released to the market, a trading halt is requested.

Since trading halts can last a maximum of 2 days, if further time is needed to suitably inform the market, the securities are suspended.

They will be reinstated once the announcement is ready to be made.