WORCESTER, Mass. - Officials in Worcester are issuing a warning after recent incidents with explosive devices found in the city. 

The Worcester County District Attorney's Office said there was a small explosion near 185 Madison Street on June 19. 

Authorities found fireworks, a gas can, and projectile materials. 

Two other non-detonated devices, made with similar materials and put inside coolers, were also discovered last month. 

Worcester Police said there are no current threats, and these devices were unsophisticated in nature. 

They are asking people to be vigilant.

The District Attorney’s Office said people should call 911 if they see unattended coolers or other suspicious items.