(Reuters) – Shares in Shaw Communications (NYSE) Inc and Rogers Communications Inc fell Monday as regulatory opposition threatened their $16 billion agreement that would have created Canada’s second-largest cellular and cable operator.

Over the weekend, the companies stated that the Canadian Competition Bureau will oppose the merger worth C$20billion due to possible effects on Canada’s wireless competition.

These concerns were addressed by the telecom companies who offered to divest Shaw’s Freedom Mobile company, the nation’s fourth-largest mobile carrier.

However, investors sold their shares early on. Shaw Communications plummeted 10% while Rogers fell 6%.

Aravinda Galappatthige, Canaccord Genuity analyst said that although there’s still some chance that the transaction will go through, it is important to acknowledge that deal risk has increased.

Rogers (NYSE:) Corp had offered to acquire Shaw Communications in exchange for C$40.50 per shares last year to expand its reach in remote areas of Western Canada. The company also wanted to compete with rivals Telus and BCE (NYSE;) Inc in a very competitive sector.

The Globe and Mail reported Friday that Shaw had asked Quebecor Inc, a telecom company to participate in a bid to acquire Shaw’s Freedom Mobile.

BCE had conditionally approved the C$3B buyout of Astral Media Inc by the Competition Bureau in 2013. This approval was made months after the offer was presented. The conditions were that Astral would make substantial divestitures of its interests in specialty and pay TV channels.