The Food and Drug Administration on Monday proposed a new framework for enforcing health and safety rules against homeopathic medicines that could lead to warning letters, involuntary seizure or criminal investigations against some companies.

The agency is focusing on a variety of homeopathic products, including those that have already reported safety concerns or that are aimed at people who are vulnerable, including people with addictions or who have cancer or heart disease. This means the FDA will more aggressively go after certain manufacturers, but under the proposal, the vast majority of homeopathic remedies would remain on the market.

The Monday announcement followed hearings and public comments from the last few years, and the draft proposal has been posted for public comment over the next 90 days. The agency will take those comments into consideration before issuing its final policy, but it did not say when that would occur.

Homeopathic drugs can come from plants, minerals and chemicals, but also from humans and animals. Homeopathic medicine is a type of alternative medicine that is based on the idea that a substance can cure a sick person if it can cause a similar sickness in a healthy person.

The industry is worth about $3 billion, and its products are sold not only online but in pharmacies and retail stores. The therapies are not regulated in the same way standard medical treatments are, due to a 1988 rule, and can go on the market without the FDA testing them to make sure they are safe and that they work.

The FDA said it would focus its enforcement efforts on products with reported safety concerns, those with possibly harmful ingredients, those taken by vulnerable populations, those aimed at helping people with serious conditions, and those that fail to meet quality and purity standards.

“In recent years, we’ve seen a large uptick in products labeled as homeopathic that are being marketed for a wide array of diseases and conditions, from the common cold to cancer. In many cases, people may be placing their trust and money in therapies that may bring little to no benefit in combating serious ailments, or worse — that may cause significant and even irreparable harm because the products are poorly manufactured, or contain active ingredients that aren’t adequately tested or disclosed to patients,” Dr. Scott Gottlieb, FDA commissioner, said in a statement.

The FDA has issued warnings about certain homeopathic drugs in recent years, including intranasal products that contain zinc and could cause people to lose some sense of smell, as well as homeopathic asthma products that haven't been shown to be effective. FDA also has warned against the homeopathic nux vomica, which has a highly toxic poison in it often used to kill mice and rats, called strychnine.

About a year ago, teething tablets and gels with the homeopathic belladonna were linked to 400 injuries, including seizures and 10 deaths.

FDA officials said they would be examining how well the agency carries out its current policies and that it plans to avail itself to those it already has at its disposal.

"We respect that some individuals want to use alternative treatments, but the FDA has a responsibility to protect the public from products that may not deliver any benefit and have the potential to cause harm," Gottlieb said.