THE investigation into the alleged breach of Stock Exchange regulations by Ming Pao Enterprise chairman Yu Pun-hoi is expected to widen. This follows the uncovering of a further offence committed by Yu while he was a student in Canada. Yu is under investigation for having failed to reveal fraud and firearms offences committed in 1979. But it has now emerged that these were not his first convictions in the country. A previously undisclosed conviction has come to light in Saskatoon, Canada. In December 1978, Yu stole goods worth C$200 from the Hudson Bay Co. department store in Saskatoon. In January 1979, he pleaded guilty to the shoplifting charge, and Judge W. L. Meagher fined him C$50. Yu paid the fine on the last day before he would have been jailed for 21 days for defaulting. In addition, the judge placed Yu on probation for 12 months and ordered him to stay out of Hudson Bay Co. stores and Canadian Tyre stores in Saskatoon for 12 months. Yu was still serving his probation when he committed a series of three cheque signature forgeries and three credit card frauds, involving a total of C$4,466.97. On March 29, 1979, he was arrested for using a stolen credit card and police found an automatic pistol in his car. Yu was convicted and was jailed for two years, less a day, for each of the three forged cheque and three credit card crimes. The sentences were served concurrently and Yu was released after serving four months. It is these offences which the Hong Kong Stock Exchange is now reviewing in its investigation into the alleged breaking of listing regulations by Yu, who did not declare them as required by company directors in Hong Kong. Last night, Herbert Hui, head of the listing division, said the Stock Exchange would look at any further evidence of crimes which Yu had not admitted to. 'We certainly intend to follow up with Yu the veracity of this latest evidence,' Mr Hui said.