Trading in the shares of UK Oil and Gas Investments has been temporarily suspended pending an announcement about the firm's Horse Hill oil reserves.
Shares were suspended on Aim from 7.30am
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"The company has requested the temporary suspension of trading in its shares, pending an announcement in relation to its interests in the Horse Hill-1 well," it said in an update to markets.
The timing of an announcement is not known.
UKOG shares gained as much as 20 per cent in intraday trading yesterday, closing down one per cent.
Shares in the company rocketed earlier this year after news of a potentially substantial oil find at the Horse Hill site near Gatwick.
Shares in oil companies also involved in the Horse Hill development - Solo Oil, Alba Minerals, Stellar Resources and Doriemus - have also been suspended pending the announcement.