Pfizer Inc.'s (PFE) shares fell as much as 6.2 percent Thursday on a Canadian newspaper report linking its arthritis drug Celebrex (search)  to 14 deaths.

But the Canadian government said it had no proof the drug caused the deaths and stock market analysts said they were not too concerned as the shares began to rebound.

"There hasn't been a causal link established," Health Canada spokeswoman Jirina Vlk said.

"It may be connected to the 14 deaths or it may not have been connected to the 14 deaths.... They could have been dying just because they were dying anyway. They could have been dying because they got hit by a bus. They could have been dying because they took some other medications."

The National Post reported on 100 adverse-reaction reports on Celebrex filed with Health Canada (search) over the past five years, including 19 cases of heart problems and five strokes. It said three million Canadian prescriptions were filled for Celebrex last year.

Officials from Pfizer were not immediately available for comment.

Celebrex has been touted as the safe alternative to Vioxx (search) after that medicine was pulled from the shelves after a study showed increase risk of heart attack and stroke.

Pfizer, a member of the Dow Jones industrial average, was off 71 cents, or 2.4 percent, at $28.74 on the New York Stock Exchange (search) after falling as low as $27.60.

"We think there is an overreaction to this news out of Canada," said Sena Lund, an analyst at Cathay Financial. "We remain less worried."

"Any news along these lines is not reassuring, but in light of the fact that these are random case reports I would not put too much weight on them," said Steve Scala, an analyst at SG Cowen. "There's a lot we don't know, and from controlled clinical studies there have not been similar results."