* Says received "tentative" inquiry about potential bid
* Says inquiry is "extremely preliminary in nature"
* Shares rise as much as 50 percent
(Adds detail)
LONDON, Sept 10 (Reuters) - British rail network services company Jarvis on Thursday said it had received a tentative approach from a potential buyer, lifting its shares by as much as 50 percent.
"The Board wishes to emphasise that although a tentative inquiry has been made about a possible offer, the inquiry is extremely preliminary in nature," Jarvis said in a statement.
Jarvis shares were up 26 percent at 23.5 pence by 1103 GMT, having earlier risen as high as 27.25 pence.
In July, Jarvis replaced its chief executive as it said one-off restructuring and redundancy costs had pushed it to an annual loss of 6.3 million pounds ($10.43 million), compared with a 4.5 million pound profit a year earlier.
(Reporting by Myles Neligan; editing by John Stonestreet)