TT organisers say bikes have been stopped entering the course due to a 'non-racing medical emergency'.
The afternoon practice session is continuing and roads remain closed.
However course action between the Grandstand and Ballacraine has been stopped to allow emergency vehicle access.
Roads around the TT course are due to open at 4.30pm as the afternoon practice session comes to an end - with the exception of the Mountain Road.
They're then due to close again at at 6pm for an evening qualifying session tonight, Wednesday, March 27 while roads are due to fully reopen no later than 9.30pm.
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