Calls in Glamis Gold shot up on Aug. 17, triggering an alert on a program measuring average daily volume of stocks and options, said Jon Najarian, founder of Chicago-based insideoptions.com.
Goldcorp said it took a lot of precaution to keep the deal under wraps.
"There certainly didn't seem to be very much happening in the stocks themselves over the past few weeks; I was actually pretty proud of how quiet we kept it and how the stocks didn't start to move," said Ian Telfer, chief executive of Goldcorp.
"Your fear in these deals is if there is a real leak, the target company stocks starts to jump up and it takes away the premium you are trying to offer their shareholders," he said.
Glamis said it is monitoring the situation.
"There are many regulatory authorities that I assume will look into all trading surrounding this deal and not just options," said Jeff Wilhoit, director of investor relations with Glamis.
Najarian said: "We don't have proof, we just have a strong suspicion that those trades on that date match the pattern of insider information being gathered and acted upon."
"On this day we saw no catalyst such as an earning announcement, or any other known event. When we see action without a known catalyst, it makes us suspicious. Someone knew something the rest of the world did not," he added.
Equity calls are contracts that give market players the right to buy the underlying security at a specific time and price in anticipation that the stock will rise.
Shares of Glamis shot up 17.9 percent on Thursday, the day it was announced that Vancouver-based Goldcorp will buy Glamis in a deal now valued at $7.6 billion
