A sharp rise in visits to emergency rooms and calls to poison control centers nationwide has some health officials fearing that more potent and dangerous variations of a popular drug known as spice have reached the nation’s streets, resulting in several deaths.

In the first three weeks of April, state poison control centers received about 1,000 reports of adverse reactions to spice — the street name for a family of synthetic substances that mimic the effects of marijuana — more than doubling the total from January through March, according to the American Association of Poison Control Centers.

The cases, which can involve spice alone or in combination with other substances, have appeared four times as often this year as in 2014, the organization said. On Thursday alone there were 172 reports, by far the most in one day this year.

Health departments in Alabama, Mississippi and New York have issued alerts this month about more spice users being rushed to hospitals experiencing extreme anxiety, violent behavior and delusions, with some of the cases resulting in death. Similar increases have occurred in Arizona, Florida, New Jersey and Texas.