CHICAGO -- Attorneys for families who lost their pets to tainted dog and cat food amended a class-action lawsuit that was filed last week, claiming that the company involved may be trying to cover up what actually happened.

Video: Pet Owners In Tailspin

NBC5's Charlie Wojciechowski reported that the lawsuit was being amended on Wednesday in an effort to hold the companies involved more responsible. Attorneys said they believe the number of animals who died from eating the contaminated food were likely closer to more than 3,000 pets, not the 15 or 16 currently being reported by the Food and Drug Administration.

Nearly 100 store and major-brand pet foods were recalled by manufacturer Menu Foods Inc. on March 16. Three other companies have recalled some foods since then. Menu Foods officials were unavailable for comment, and its Web site was last updated March 16, Wojciechowski reported. Illinois Sen. Dick Durbin has scheduled an afternoon news conference on Thursday to announce that he would hold hearings on the pet food recall.

Attorneys said Menu Foods tried to cover up evidence of tainted food. Attorneys said Menu Foods first began hearing reports of sick pets in December of last year, but didn't begin testing animals until late February. On March 6, it found a new supplier of the now-suspect wheat gluten, attorneys said, but it took another 10 days to announce a recall.

"We think that it actually rises to the level of fraud," said attorney Jay Edelson.

Dawn Majerczyk, who is part of the class-action lawsuit, said she broke down when her cat Phoenix died, saying at first she felt responsible when he took a sudden turn for the worse last month. But when news of the Menu Food recall began to filter out, she felt angry.

"I thought I killed my cat," she said. "I did this, I fed it. To realize, no, this wasn't me, this is the neglect out there."

Rick Kancillja's prized tabby cat, Angel, died from kidney failure, Wojciechowski reported, two days after the recall.

"I just held her for four hours up against me," he said. "I was crying, crying, crying, I just could not believe it. She was my best friend, she was my source of joy."

One thing especially upsetting to many pet owners was that they bought the food because of the reputation of the company, only to find out that the food was not made by that particular company.

Ben Delong thought the premium food he was feeding his cat Freddy was made by Iams, but it has been included in the recall. Delong said someone at the company should be held responsible.

"So far, we've spent $2,000, and every time I go in to get her blood work, it's $181," he said.