(Canadian Press) Stock in TMX Group Inc.(TSX:T.X, Stock Forum) was down sharply Monday in a move one well-known investor said was probably linked to arbitragers divesting their positions in the recently-acquired owner of the Toronto Stock Exchange.

"My sense is the arbitragers are unwinding — that would be my guess," said Tom Caldwell, chairman and CEO of Caldwell Financial, after shares in the operator of Canada's major stock exchanges fell more than 10% in early trading.

The issue later recovered a little and by midday was down 8.9%, at $45.31 a share.

The big drop, on relatively low volume, came on the first trading day since Friday's announcement that the long-extended, $50 per share offer by Maple Group Acquisition Corp.— a consortium of 12 Canadian financial institutions formed for the bid.

By the Friday deadline, some 95.4% of outstanding TMX Group shares had been tendered to the offer, worth a total of about $3.8 billion.

Under deals made with provincial and federal securities regulators, Maple pledged that it would not own more than 80% of TMX shares — leaving 20 per cent in public hands.

To maintain the promise, Maple, now the owner of the recently renamed TMX Group Ltd., will return the 15.4% of shares tendered but not acquired to TMX Group shareholders.

All shares that weren't picked up by Maple, now TMX Group Ltd., will be exchanged for shares of the successor company on a one-for-one basis.

The offer by Maple, a consortium of Canadian banks, pension funds and investment firms, cleared its last major regulatory hurdles when the federal Competition Bureau and securities regulators in B.C. and Alberta signed off on the takeover last month.

Arbitragers who bought TMX stock in order to tender it to the offer would have, in many cases, acquired their positions several weeks ago at around $45 a share before the regulatory votes.