ST. PETERSBURG, FL — Following a rash of overdose calls related to what is believed to be synthetic marijuana, St. Petersburg Police Officers planned on hitting the streets Monday to warn of the dangers of the illegal substance.

Synthetic marijuana, also known as "spice," is suspected in a string of overdoses that have been reported in the city and in nearby communities since Thursday. As of Monday morning, the St. Petersburg Police Department said its number of overdose calls had climbed to 28. Some of the calls included multiple victims, the agency noted in an email to media. "It appears a particular batch of spice is causing some people to have a severe reaction," the email said. "Our officers were out spreading the word on the street to stay away from spice."

Spice contains a mix of herbs and chemicals meant to mimic the effects of other drugs, such as marijuana. Often packaged to be attractive to children, many of the ingredients used in spice production are illegal in Florida. The city of Clearwater has also reported an uptick in spice-related issues. Police there conducted a Sunday sweep at a local park that resulted in several arrests related to suspected spice possession.

Overdoses reported to date have not resulted in death or serious medical issues, police said. The symptoms St. Petersburg police have seen so far range from vomiting and seizures to unconsciousness. Four spice-related arrests were made in St. Petersburg over the weekend, as well.